Systems and methods for positioning multiple trimmable marine propulsion devices on a marine vessel

Abstract

A controller carries out a method for positioning multiple trimmable marine propulsion devices on a marine vessel transom. The method includes identifying two propulsion devices located one on either side of a transom centerline and defining these as outer propulsion devices. A third propulsion device coupled to the transom between the outer propulsion devices is defined as an inner propulsion device. A user input is received to trim the outer and inner propulsion devices in a single direction with respect to their current trim angles. In response to the user input, the controller outputs a control signal. In response to the control signal, the outer propulsion devices are trimmed in the single direction to a first trim angle and the inner propulsion device is trimmed in the single direction to a second, different trim angle. The controller may rate limit trimming of the outer propulsion devices to accomplish this.

Claims

1. A method for positioning at least three trimmable marine propulsion devices coupled to a transom of a marine vessel, the method being carried out by a controller and comprising: identifying two propulsion devices located one on each of a port side and a starboard side of a vertical centerline of the transom and spaced symmetrically with respect to the centerline of the transom; defining the two propulsion devices as outer propulsion devices; identifying a third propulsion device coupled to the transom between the outer propulsion devices; defining the third propulsion device as an inner propulsion device; receiving a user input to trim each of the outer and inner propulsion devices in a single direction with respect to current trim angles of each of the outer and inner propulsion devices; and in response to the user input, outputting a control signal; and in response to the control signal, trimming the outer propulsion devices in the single direction to a first trim angle and trimming the inner propulsion device in the single direction to a second trim angle that is different from the first trim angle.

2. The method of claim 1, wherein the first trim angle is less than the second trim angle.

3. The method of claim 2, further comprising trimming the outer propulsion devices in the single direction at a first rate, and trimming the inner propulsion device in the single direction at a second rate that is faster than the first rate.

4. The method of claim 3, further comprising trimming both the inner propulsion device and the outer propulsion devices for a same amount of time.

5. The method of claim 3, wherein the outer propulsion devices are respectively coupled to first and second hydraulic piston-cylinders controlled by respective first and second flows of hydraulic fluid from respective first and second hydraulic pump-motors, and the inner propulsion device is coupled to a third hydraulic piston-cylinder controlled by a third flow of hydraulic fluid from a third hydraulic pump-motor.

6. The method of claim 5, further comprising pulse width modulating the control signal such that first and second pulse width modulated (PWM) signals controlling the respective first and second hydraulic pump-motors are the same as one another, but are different from a third PWM signal controlling the third hydraulic pump-motor.

7. The method of claim 5, further comprising supplying first and second voltages to the respective first and second hydraulic pump-motors that are the same as one another, and supplying a third voltage to the third hydraulic pump-motor that is different from the first and second voltages.

8. The method of claim 5, further comprising providing first, second, and third hydraulic rate limiters for each of the respective first, second, and third hydraulic piston-cylinders, and limiting the first and second flows of hydraulic fluid to the respective first and second hydraulic piston-cylinders differently than the third flow of hydraulic fluid to the third hydraulic piston-cylinder.

9. The method of claim 1, wherein a fourth propulsion device is coupled to the transom of the marine vessel between the outer propulsion devices, and further comprising: defining the third and fourth propulsion devices as inner propulsion devices; and in response to the user input, outputting the control signal, in response to which the inner propulsion devices are trimmed in the single direction to the second trim angle.

10. The method of claim 1, further comprising trimming each of the inner and outer propulsion devices simultaneously in response to the control signal.

11. The method of claim 1, further comprising generating and outputting the control signal in response to a single user input for as long as the single user input is received.

12. The method of claim 1, further comprising outputting the control signal in response to the user input only if the marine vessel is operating above a threshold speed upon receipt of the user input.

13. A method for positioning at least three trimmable marine propulsion devices coupled to a transom of a marine vessel, the method being carried out by a controller and comprising: identifying two propulsion devices located one on each of a port side and a starboard side of a vertical centerline of the transom and spaced symmetrically with respect to the centerline of the transom; defining the two propulsion devices as outer propulsion devices; identifying a third propulsion device coupled to the transom between the outer propulsion devices; defining the third propulsion device as an inner propulsion device; receiving a user input to trim each of the outer and inner propulsion devices in a single direction; in response to the user input, outputting a control signal; in response to the control signal, trimming each of the outer and inner propulsion devices simultaneously in the single direction for a same amount of time; and limiting a first rate at which the outer propulsion devices trim in the single direction more than a second rate at which the inner propulsion device trims in the single direction.

14. The method of claim 13, wherein the outer propulsion devices are respectively coupled to first and second hydraulic piston-cylinders controlled by respective first and second flows of hydraulic fluid from respective first and second hydraulic pump-motors, and the inner propulsion device is coupled to a third hydraulic piston-cylinder controlled by a third flow of hydraulic fluid from a third hydraulic pump-motor.

15. The method of claim 14, further comprising pulse width modulating the control signal such that first and second pulse width modulated (PWM) signals controlling the respective first and second hydraulic pump-motors are the same as one another, but are different from a third PWM signal controlling the third hydraulic pump-motor.

16. The method of claim 14, further comprising supplying first and second voltages to the respective first and second hydraulic pump-motors that are the same as one another, and supplying a third voltage to the third hydraulic pump-motor that is different from the first and second voltages.

17. The method of claim 14, further comprising providing first, second, and third hydraulic rate limiters for each of the respective first, second, and third hydraulic piston-cylinders, and limiting the first and second flows of hydraulic fluid to the respective first and second hydraulic piston-cylinders differently than the third flow of hydraulic fluid to the third hydraulic piston-cylinder.

18. The method of claim 13, further comprising generating and outputting the control signal in response to a single user input for as long as the single user input is received.

19. The method of claim 13, further comprising outputting the control signal in response to the user input only if the marine vessel is operating above a threshold speed upon receipt of the user input.

20. A system for a marine vessel, the system comprising: first and second propulsion devices located one on each of a port side and a starboard side of a vertical centerline of a transom of the marine vessel and spaced symmetrically with respect to the centerline of the transom; a third propulsion device coupled to the transom between the first and second propulsion devices; a controller that defines the first and second propulsion devices as outer propulsion devices and defines the third propulsion device as an inner propulsion device; a user input device in signal communication with the controller; and first, second, and third trim actuators coupled to and rotating the first, second, and third propulsion devices, respectively; wherein the controller is in signal communication with the first, second, and third trim actuators; and wherein in response to a single command from the user input device, the controller outputs control signals to the first and second trim actuators, which thereafter trim the outer propulsion devices in a given direction to a first trim angle, and the controller outputs a control signal to the third trim actuator, which thereafter trims the inner propulsion device in the given direction to a second trim angle that is different from the first trim angle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure is described with reference to the following Figures. The same numbers are used throughout the Figures to reference like features and like components.

(2) FIG. 1 illustrates one example of a transom of a marine vessel shown from a top view with three outboard motors coupled thereto.

(3) FIG. 2 shows a schematic rear view of a V-shaped transom with three propeller outlines illustrated thereon.

(4) FIG. 3 illustrates a system for controlling trim angles of four outboard motors coupled to a transom of a marine vessel.

(5) FIG. 4 illustrates a prior art method for trimming three or more marine propulsion devices.

(6) FIG. 5 illustrates a method according to the present disclosure for trimming three or more marine propulsion devices.

(7) FIG. 6 is a schematic showing trimming of four propulsion devices.

(8) FIG. 7 shows an example of a user input device for inputting trim commands.

(9) FIG. 8 illustrates another method according to the present disclosure for trimming three or more marine propulsion devices.

(10) FIG. 9 illustrates yet another method according to the present disclosure for trimming three or more marine propulsion devices.

DETAILED DESCRIPTION

(11) In the present description, certain terms have been used for brevity, clarity and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes only and are intended to be broadly construed.

(12) FIG. 1 illustrates a transom 10 of a marine vessel to which three marine propulsion devices 12a, 12b, 12c are coupled. Here, each of the propulsion devices 12a-12c is an outboard motor that is coupled to the transom 10 by way of a mounting bracket 14a-14c, as known to those having ordinary skill in the art. However, for purposes of the disclosure provided herein, the propulsion devices 12a-12c could just as well be sterndrives, for example as shown and described in the above-incorporated U.S. Pat. No. 4,776,818. A first propulsion device 12a is coupled to the far port side 20 of the transom 10, a second propulsion device 12b is coupled to the far starboard side 22 of the transom 10, and a third propulsion device 12c straddles a centerline 13 of the transom 10. The propulsion devices are able to be trimmed up and down with respect to the transom 10 by way of trim actuators (such as, but not limited to, hydraulic cylinders, pneumatic cylinders, or electric-linear actuators) to different trim positions as shown in FIGS. 1-3 of the above-incorporated U.S. Pat. No. 7,416,456. Various types, configurations, and functionalities of trim actuators used to provide such rotation are well-known in the art, for example as in U.S. Pat. No. 4,050,359, incorporated by reference above.

(13) The present disclosure provides methods for controlling multiple trim actuators that trim two, three, or more propulsion devices coupled to a transom of a marine vessel, for reasons that will be discussed with respect to FIG. 2. In FIG. 2, a V-shaped hull 16 of a marine vessel is shown schematically with the outlines of three propellers 18a, 18b, 18c outlined as they would appear from a rear view of the transom 10. Because the majority of vessel installs desire the visual aesthetics of propulsion devices that are mounted level with one another, typically, the marine propulsion devices 12a-12b to which the propellers 18a-18c are coupled will be installed at the same height on the transom 10. Additionally, the majority of propulsion devices will be mounted symmetrically with respect to the centerline 13 of the transom 10, such that a distance D between the centerline 13 and the rotation axis 19a, 19b of each propeller 18a, 18b of a propulsion device 12a, 12b on either side of the centerline 13 is the same. However, especially for non-flat bottomed hulls, the combination of dead rise, drive separation, and, for example, five-inch gear case increments will typically result in unequal propeller areas working on the water if the propulsion devices are installed level with one another and also trimmed to the same level. This results in less than optimal vessel performance.

(14) For example, in FIG. 2, the device to which propeller 18a is coupled is trimmed higher than that to which propeller 18b is coupled, and the two propellers 18a, 18b do not have the same area in the water. Propellers 18c and 18c show the same device being trimmed to different levels, where propeller 18c is trimmed lower than propeller 18c. The device to which propeller 18a is coupled is trimmed the same as that to which propeller 18c is coupled, but the two propellers do not have the same area in the water. In contrast, the propellers 18a and 18c do have the same area in the water, despite the fact that the device to which propeller 18c is coupled is trimmed to a higher trim position than that of 18a. Note also that the propellers 18b and 18c have the same area in the water, even though they are not trimmed to the same position.

(15) Further, hull designs that include pads, setbacks and/or unique notches can also contribute to the effect that a given propeller will have on producing thrust to propel the marine vessel as well as on adjusting its attitude in the water. Nonetheless, most operators simply use a trim-all button (that trims each of the three, four, or more propulsion devices to the same trim position) and accept less than optimized running behavior, or they manually command each propulsion device independently to an optimized trim angle using three or four separate buttons, which takes time and requires a free hand. Not performing this individual trim and thus introducing differential trim between pairs of inner and outer propulsion devices can have negative effects on the performance of the system and can induce additional electromechanical wear. The present inventors realized that because vessels equipped with three or more marine propulsion devices typically benefit from different trim angles between pairs of outer and inner propulsion devices for optimal efficiency, user controls could be provided to achieve differentially trimmed propulsion devices in a faster, easier, and more intuitive way. The present inventors discovered that trimming both devices in a given pair in the same manner is efficient, because each propulsion device in a pair is at the same level on the transom 10 as the other and is equally spaced from the keel. Thus, the propulsion devices in one pair can be treated independently from the propulsion devices in another pair (or from a single, centrally-located propulsion device) without fear of substantially upsetting the roll or steering of the vessel.

(16) For example, FIG. 3 shows an instance in which four propulsion devices 12a-12d are provided on the transom 10 of a marine vessel by way of mounting brackets 14a-14d. It can be seen from study of FIG. 2 that it may be desirable to trim up the inner propulsion devices (12c and 12d) on a V-shaped hull more than the propulsion devices towards the outer edges (12a and 12b) of a V-shaped hull. (Recall that propellers 18a and 18c have the same area in the water and that the device to which propeller 18c is coupled is trimmed to a higher trim position than that of 18a.) Trimming the inner propulsion devices 12c and 12d on a V-shaped hull more than the outer propulsion devices 12a and 12b (for example, see FIG. 6) would ensure that the propellers of each of the propulsion devices 12a-12d have a roughly equivalent area in the water and therefore a roughly equivalent effect on positioning and propelling the vessel, all else being equal. Similar principles apply to hulls of different shapes other than that shown herein.

(17) According to the present disclosure, a system and method are provided for accepting a user input to trim each of the outer and inner propulsion devices in a single direction with respect to their current trim angles (i.e., all devices are trimmed up or all are trimmed down), and in response to the user input, outputting a trim control signal with a controller to trim the outer propulsion devices 12a, 12b in the single direction to a first trim angle and to trim the inner propulsion devices 12c, 12d in the single direction to a second, different trim angle. This may be done by rate-limiting the trimming of the outer propulsion devices 12a, 12b in comparison to the trimming of the inner propulsion devices 12c, 12d. Examples of such a system and several methods for achieving the resulting paired differential trim angles of the propulsion devices will be described herein below.

(18) FIG. 3 shows a schematic of a system 24 associated with the marine vessel. In the example shown, the system 24 includes a controller 26, which is programmable and includes a processor 28 and a memory 30. The controller 26 can be located anywhere in the system 24 and/or located remote from the system 24 and can communicate with various components of the marine vessel via wired and/or wireless links, as will be explained further herein below. Although FIG. 3 shows one controller 26, the system 24 can include more than one controller. For example, the system 24 can have controllers located at or near a helm of the marine vessel and can also have controllers located at or near the propulsion devices 12a-12d. Portions of the method disclosed herein below can be carried out by a single controller or by several separate controllers. Each controller can have one or more control sections or control units. One having ordinary skill in the art will recognize that the controller 26 can have many different forms and is not limited to the example that is shown and described. For example, a single controller 26 is shown as carrying out the trim control method for all propulsion devices 12a-12d, but in other examples separate controllers could be provided for each propulsion device.

(19) In some examples, the controller 26 may include a computing system that includes a processing system, storage system, software, and input/output (I/O) interfaces for communicating with devices such as those shown in FIG. 3, and about to be described herein. The processing system loads and executes software from the storage system, such as software programmed with a trim control method. When executed by the computing system, trim control software directs the processing system to operate as described herein below in further detail to execute the trim control method. The computing system may include one or many application modules and one or more processors, which may be communicatively connected. The processing system can comprise a microprocessor (e.g., processor 28) and other circuitry that retrieves and executes software from the storage system. Processing system can be implemented within a single processing device but can also be distributed across multiple processing devices or sub-systems that cooperate in existing program instructions. Non-limiting examples of the processing system include general purpose central processing units, applications-specific processors, and logic devices.

(20) The storage system (e.g., memory 30) can comprise any storage media readable by the processing system and capable of storing software. The storage system can include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. The storage system can be implemented as a single storage device or across multiple storage devices or sub-systems. The storage system can further include additional elements, such as a controller capable of communicating with the processing system. Non-limiting examples of storage media include random access memory, read only memory, magnetic discs, optical discs, flash memory, virtual memory, and non-virtual memory, magnetic sets, magnetic tape, magnetic disc storage or other magnetic storage devices, or any other medium which can be used to store the desired information and that may be accessed by an instruction execution system. The storage media can be a non-transitory or a transitory storage media.

(21) In this example, the controller 26 communicates with one or more components of the system 24 via a communication link 32, which can be a wired or wireless link. The controller 26 is capable of monitoring and controlling one or more operational characteristics of the system 24 and its various subsystems by sending and receiving control signals via the communication link 32. In one example, the communication link 32 is a controller area network (CAN) bus, but other types of links could be used. It should be noted that the extent of connections of the communication link 32 shown herein is for schematic purposes only, and the communication link 32 in fact provides communication between the controller 26 and each of the devices described herein, although not every connection is shown in the drawing for purposes of clarity.

(22) In the example shown, the controller 26 receives commands from a user input device 34 such as a keypad or a touchscreen. The user input device 34 includes an interface having trim up buttons 36 that command the propulsion devices 12a-12d to rotate relatively up out of the water and trim down buttons 38 that command the propulsion devices 12a-12d to rotate relatively further down into the water. If the user input device 34 is a touchscreen, it can include buttons in the traditional sense or selectable screen icons. The touchscreen could also display information about the system 24 to the operator of the vessel, such as engine speed, vessel speed, trim angle of each propulsion device, trim operating mode, vessel acceleration rate, etc. An example of the user input device 34 is provided in FIG. 7 and will be described further herein below.

(23) The system 24 also includes first and second propulsion devices 12a, 12b located one on each of a port side 20 and a starboard side 22 of a vertical centerline 13 of the transom 10 of the marine vessel and spaced symmetrically with respect to the centerline 13 of the transom 10. The controller 26 identifies these propulsion devices 12a, 12b via the communication link 32 and defines them as outer propulsion devices. Third and fourth propulsion devices 12c, 12d are also coupled to the transom 10 between the outer propulsion devices 12a, 12b. The controller 26 defines these as inner propulsion devices. If only one propulsion device is provided between the outer propulsion device 12a, 12b (see FIG. 1), the controller 26 defines this as a single inner propulsion device 12c. It should be understood that each time the inner propulsion devices are referred to in the plural herein below, the description applies equally to a single, central propulsion device unless otherwise noted. Additionally, the same principles discussed herein below apply equally to systems equipped with five or six propulsion devices.

(24) First, second, third, and fourth trim actuators 39a-39d are coupled to and rotate the first, second, third, and fourth marine propulsion devices 12a-12d, respectively, about horizontal tilt-trim axes, as is known. In this example, hydraulic piston-cylinders 40a-40d, in fluid communication with hydraulic pump motors 48a-48d, are coupled to and rotate the propulsion devices 12a-12d. Each piston-cylinder 40a-40d has a rod 42a-42d, which, on the free end shown, is connected to a respective propulsion device 12a-12d. The opposite end of each rod 42a-42d is connected to a piston 44a-44d that moves within a cylinder 46a-46d in response to flow of hydraulic fluid from respective first, second, third, and fourth hydraulic pump-motors 48a-48d. The controller 26 is also in signal communication with the hydraulic pump-motors 48a-48d and sends control signals to trim-out relays 50a-50d or trim-in relays 52a-52d to switch flow of hydraulic fluid through the hydraulic pump-motors 48a-48d. The controller 26 controls energizing of solenoids in the relays 50a-50d and 52a-52d, which act as switches to couple a power source such as a battery (not shown) to the pump-motors 48a-48b. In other examples, the trim-in relays 52a-52d and the trim-out relays 50a-50d are each a single relay that can turn an individual pump-motor 48-48d on or off. In still another example, the piston-cylinders are electrically-actuated, and the trim-in relays 52a-52d and the trim-out relays 50a-50d can effect a trim-in or trim-out movement of the piston-cylinders 40a-40d directly.

(25) First hydraulic lines 54a-54d couple the pump-motors 48a-48d to first chambers 56a-56d of the piston-cylinders 40a-40d, and second hydraulic lines 58a-58d couple the pump-motors 48a-48d to second chambers 60a-60d of the piston-cylinders 40a-40d. As long as the trim-in relays 52a-52d are activated, the pump-motors 48a-48d provide hydraulic fluid through the first hydraulic lines 54a-54d to the first chambers 56a-56d of the piston-cylinders 40a-40d, thereby pushing the pistons 44a-44d downwardly within the cylinders 46a-46d and lowering (trimming in) the propulsion devices 12a-12d coupled to the rods 42a-42d. As long as the trim-out relays 50a-50d are activated, the pump-motors 48a-48c provide hydraulic fluid through the second hydraulic lines 58a-58d to the second chambers 60a-60c of the piston-cylinders 40a-40c, thereby pushing the pistons 44a-44c upwardly within the cylinders 46a-46c and raising (trimming out) the propulsion devices 12a-12d coupled to the rods 42a-42d. Hydraulic fluid can be removed from the opposite chambers 56a-56d or 60a-60d of the cylinders 46a-46d into which fluid is not being pumped in either instance, and drained to a tank or re-circulated through the pump-motors 48a-48d.

(26) Referring now to FIGS. 4 and 7, according to prior art systems and methods, to prepare for launch, an operator would first press a trim-all down button 64b, as shown at 400, while operating at low or idle speeds. As shown at 402, the outer propulsion devices 12a, 12b and inner propulsion devices 12c, 12d would thereafter simultaneously trim to the same trim angle, which in this is example is fully down, in preparation for launch. The operator would then accelerate to planing speed, as shown at 404. After planing speed is reached, he would then press a trim-all up button 64a as shown at 406 to simultaneously trim all of the propulsion devices 12a-12d to a single trim position calibrated for relatively better performance of the vessel, considering the constraint that all propulsion devices would be trimmed to the same position, as shown at 408. If the operator wished to adjust the trim for either the inner or outer propulsion devices separately beyond this position, he would next press two or more separate buttons in order to trim just the inner or just the outer propulsion devices. For example, he would press two or more trim up buttons 68a, 70a, as shown at 410, to trim the inner propulsion devices 12c, 12d, as shown at 412. He would also need to press two or more trim up buttons 72a, 74a, as shown at 416, to trim the outer propulsion devices 12a, 12b, as shown at 418. Thus, it can be seen that while the use of a button such as the trim-all up button 64a as shown at 406 makes operation somewhat easier for an inexperienced operator, the concurrent acts of steering and throttling the vessel result in few free additional movements available to input subsequent trim commands. Therefore, when a more experienced operator desired to trim pairs of propulsion devices separately after using the trim-all up button 64a as shown at 406, he would need to leave one of the pairs of propulsion devices at the original trim-all position while he used a free hand to trim the other pair. This resulted in less than optimal performance of the vessel, and required a number of distinct steps.

(27) In contrast, according to the method proposed herein and shown in FIG. 5, selection of a single button will trim a pair of propulsion devices to a trim angle that is unique from the other pair of propulsion devices' trim angle. According to the present method, while operating in idle or at low speeds, an operator may select a button such as the trim-all down button 64b as shown at 500. Thereafter, the outer propulsion devices 12a, 12b and inner propulsion devices 12c, 12d will be trimmed to the same fully down position, as shown at 502. As the operator accelerates to planing speed, a new process for adjusting trim for all of the propulsion devices 12a-12d simultaneously such that optimal performance is achieved can be initiated by pressing a single trim-all up button 64a, as shown at 506. In response to the single user input, the controller 26 can output a control signal that achieves differentially trimmed pairs of propulsion devices in one of a few ways. One example is by rate limiting trimming of the outer propulsion devices 12a, 12b separately from the inner or single propulsion device(s) 12c, 12d such that the propulsion devices 12a-12d trim in pairs at different rates. This is shown at 508 in FIG. 5. The rates can be set such that the pairs reach different trim angles simultaneously. The end result, however, is that the outer pair of propulsion devices 12a, 12b is trimmed to a first trim angle and the inner pair (or single) propulsion device(s) 12c, 12d is/are trimmed to a second trim angle that is different from the first trim angle, as shown at 510. In one example, as shown in FIG. 6, the first trim angle A1 as measured from a fully down position 76 is less than the second trim angle A2 as measured from the fully down position 76, where 78 represents an upper trim angle limit.

(28) The method disclosed may be enabled only while the vessel is underway, where it is of use to reduce electromechanical wear on the components associated with trimming the marine propulsion devices 12a-12d. For example, the method may include outputting the control signal in response to the user input only if the marine vessel is operating above a threshold speed upon receipt of the user input. The threshold speed might be, for example, approximately the planing speed calibrated for that particular vessel. In other words, the method would not necessarily be able to be performed at idle or key-on/engine-off. Additionally, it should be noted that the methods described herein can be implemented completely separately from a full auto-trim control method, in which propulsion devices are automatically trimmed to given setpoints depending on vessel or engine speed. Rather, the methods described herein are carried out in response to commands input manually via the user input device 34 (FIG. 7).

(29) Different devices and/or programming can be introduced into the system 24 to manipulate the signal between the controller 26 and the trim system in such a way that the result is differently-trimmed pairs of propulsion devices. For example, ways to implement a rate limiter will now be described. While the below examples are discussed with respect to hydraulic trim cylinders, those having skill in the art will realize that corresponding devices and methods exist for rate-limiting pneumatically or electrically actuated trim cylinders. One rate-limiting method is a pulse width modulation (PWM) method, in which the controller 26 pulse width modulates the control signal from the controller 26 to the hydraulic pump-motors 48a-48d such that first and second PWM signals controlling the respective first and second hydraulic pump-motors 48a, 48b are the same as one another, but are different from a third PWM signal controlling the third hydraulic pump-motor 48c and from a fourth PWM signal controlling the fourth hydraulic pump-motor 48d. Note that the third and fourth PWM signals would be the same as one another. In this example, the duty cycle of the signals sent to the first and second hydraulic pump-motors 48a, 48b would be less than the duty cycle of the signals sent to the third and fourth hydraulic pump-motors 48c, 48d.

(30) Another example is by buffering the hydraulic system, such as by introducing hydraulic rate limiters for each trim actuator (e.g. variable orifices, variable flow control valves, fixed orifices) that control the flow of hydraulic fluid from the pump-motors 48a-48d to the piston-cylinders 40a-40c. For example, hydraulic rate limiters (see first and second hydraulic rate limiters 62a, 62b, FIG. 3) could be provided for a pair (or all) of the respective first, second, third, and fourth hydraulic piston-cylinders 40a-40d. The controller could control the size of the orifices (or the orifices could be fixed at different sizes) such that first and second flows of hydraulic fluid to the respective first and second hydraulic piston-cylinders 40a, 40b are limited differently than third and fourth flows of hydraulic fluid to the third and fourth hydraulic piston-cylinders 40c, 40d. In this example, flow to the first and second hydraulic piston-cylinders 40a, 40b would be less than flow to the third and fourth hydraulic piston-cylinders 40c, 40d.

(31) Another example is by buffering the electrical signal or the power to the pump-motors 48a-48c, such as by providing different voltages (for example by using a voltage buffer amplifier) to each of the motors controlling the trim pumps. For example, the controller 26 could supply first and second voltages to the respective first and second hydraulic pump-motors 48a, 48b that are the same as one another, and could supply third and fourth voltages to the third and fourth hydraulic pump-motors 48c, 48d that are different from the first and second voltages. Note that the third and fourth voltages would be the same as one another. In this example, voltage to the first and second hydraulic piston-cylinders 40a, 40b would be less than voltage to the third and fourth hydraulic piston-cylinders 40c, 40d.

(32) The controller 26 can be programmed such that the propulsion devices 12a-12d trim simultaneously. For example, referring to FIG. 6, the present method can include trimming both the inner propulsion devices 12c, 12d and the outer propulsion devices 12a, 12b for the same amount of time, but at different rates. The time it takes for the outer propulsion devices 12a, 12b to reach the first trim angle A1 may be the same as the time it takes for the inner propulsion devices 12c, 12d to reach the second trim angle A2, but the distance to reach the first trim angle A1 is not equal to the distance to reach the second trim angle A2. This shown by the inner propulsion devices 12c, 12d traveling a distance D2 from the fully down position 76 in the same amount of time T as the outer propulsion devices 12a, 12b travel a shorter distance D1. Thus, the method may include trimming the outer propulsion devices 12a, 12b in the single direction at a first rate, and trimming the inner propulsion devices 12c, 12d in the single direction at a second rate that is faster than the first rate. This method need not include a feedback loop to achieve the desired trim angles, but could be controlled in an open loop manner.

(33) Referring to FIGS. 3 and 7, the controller 26 can be programmed such that a single touch of one of the trim-all buttons 64a or 64b trims the propulsion devices 12a-12d up or down for a pre-determined given amount of time. For example, a single touch of one of the trim-all buttons 64a or 64b might energize the trim relays 50a-50d or 52a-52d for a given number of seconds. In another example, the controller 26 may be programmed such that it generates and outputs the control signal in response to a single user input for as long as the user input is received. In other words, the controller 26 may activate the trim-in relays 52a-52d or trim-out relays 50a-50d for as long as the operator's finger remains on one of the trim-all buttons 64a or 64b. Both of the above methods would be controlled in an open loop manner. The controller 26 may trim the propulsion devices consecutively, such that one pair trims before the other, or may trim the propulsion devices simultaneously, as described with respect to FIG. 6. In yet another example, the controller 26 does not trim the propulsion devices for the same amount of time, but rather for a given amount of time each, yet at the same rate, again using open loop control. In still another example, the controller 26 delays trimming the outer propulsion devices 12a, 12b up in response to actuation of the trim-all up button 64a by a given amount of time, in order that when the outer propulsion devices 12a, 12b do begin trimming at the same rate as the inners, they do not trim to as high an angle as the inner propulsion devices 12c, 12d trim.

(34) The process for determining the trim angles to which each of the propulsion devices 12a-12d is to be trimmed is not a focus of the present disclosure. There are numerous prior art methods for determining differential trim position setpoints. Ideally, the trim angle differential between inner and outer pairs of propulsion devices will be calibrated per vessel, and stored in the memory 30 of the controller 26 for that particular vessel. In other examples, the angle differential might be able to be set by the operator via the user input device 34. Nonetheless, the methods disclosed herein can be considered to cover comparison of desired trim setpoint angles between the outer and inner pairs with one another. Benefits of such a method include less battery usage and less trim system deterioration due to trim stall. For example, if all propulsion devices 12a-12d are programmed to reach a fully down trim angle at approximately the same time as one another when trim-down is initiated, it is unlikely any one of the trim systems will stall due to inability to reach the setpoint.

(35) In another example, the user input device 34 includes a sync button 80 (FIG. 7) that allows the operator to turn the differential trim capabilities on and off. If the differential trim capabilities are turned off, the operator can use the trim-all buttons 64a, 64b in the usual manner, to trim each of the three or four propulsion devices simultaneously at the same rate and to the same trim angle.

(36) Therefore, one method according to the present disclosure is shown in FIG. 8, and includes identifying two propulsion devices 12a, 12b located one on each of a port side 20 and a starboard side 22 of a vertical centerline 13 of the transom 10 and spaced symmetrically with respect to the centerline 13 of the transom 10, as shown at 800. The method includes defining the two propulsion devices 12a, 12b as outer propulsion devices, as shown at 802. The method also includes identifying a third propulsion device 12c coupled to the transom 10 between the outer propulsion devices 12a, 12b, as shown at 804, and defining the third propulsion device 12c as an inner propulsion device, as shown at 806. If a fourth propulsion device 12d is provided on the transom 10, the fourth propulsion device 12d is also identified and defined as an inner propulsion device. At 808, a user input is received to trim each of the outer and inner propulsion devices 12a-12d in a single direction with respect to current trim angles of each of the outer and inner propulsion devices 12a-12d. In response to the user input, a controller 26 outputs a control signal that trims the outer propulsion devices 12a, 12b in the single direction to a first trim angle D1 and trims the inner propulsion devices 12c, 12d in the single direction to a second trim angle D2 that is different from the first trim angle D1, as shown at 810. See also FIG. 6.

(37) Another method according to the present disclosure is shown in FIG. 9. A controller 26 identifies two propulsion devices 12a, 12b located one on each of a port side 20 and a starboard side 22 of a vertical centerline 13 of the transom 10 and spaced symmetrically with respect to the centerline 13 of the transom 10, as shown at 900, and defines the two propulsion devices 12a, 12b as outer propulsion devices, as shown at 902. The method includes identifying a third propulsion device 12c coupled to the transom 10 between the outer propulsion devices 12a, 12b, as shown at 904, and defining the third propulsion device 12c as an inner propulsion device, as shown at 906. If a fourth propulsion device 12d is provided on the transom 10, the fourth propulsion device 12d is also identified and defined as an inner propulsion device. The method includes receiving a user input to trim each of the outer and inner propulsion devices 12a-12d in a single direction, as shown at 908. In response to the user input, the method includes outputting a control signal that trims each of the outer and inner propulsion devices 12a-12d simultaneously in the single direction for a same amount of time, as shown at 910. The controller 26 limits a first rate at which the outer propulsion devices 12a, 12b trim in the single direction more than a second rate at which the inner propulsion devices 12c, 12d trim in the single direction, as shown at 912.

(38) Thus far, the method has been discussed and described with respect to trimming the propulsion devices 12a-12d up from their fully down position once the vessel is on-plane. However, similar principles apply to trimming the propulsion devices down while underway. If the trim angles of the propulsion devices need to be adjusted due to water conditions or vessel loading conditions while the vessel is underway in order to provide better visibility or a smoother ride, the paired differential trimming can still be maintained. For instance, in response to actuation of the trim-all down button 64b (FIG. 7), the controller 26 may cause the inner propulsion devices 12c, 12d to trim down at a rate that is faster than that at which the outer propulsion devices 12c, 12d trim down. Ideally, the rates at which the propulsion devices trim down would have the same ratio as the ratio between the rates at which they trimmed up. This way, the inner propulsion devices 12c, 12d will remain relatively higher in the water than the outer propulsion devices 12a, 12b, at least while the vessel is still planing. Trimming the inner propulsion devices 12c, 12d down faster will also allow them to reach the fully down position at the same time as the outer propulsion devices 12a, 12b, as noted above, in response to the operator commanding this once the vessel is no longer planing.

(39) In the above description, certain terms have been used for brevity, clarity, and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. The different systems and method steps described herein may be used alone or in combination with other systems and methods. It is to be expected that various equivalents, alternatives and modifications are possible within the scope of the appended claims.