System and method for controlling position of a marine drive

Abstract

A method of controlling a marine drive on a marine vessel includes receiving a trim position instruction to adjust a trim position of the marine drive, receiving a steering position of the marine drive, determining an allowable steering angle range based on the trim position instruction and/or the adjusted trim position of the marine drive, and controlling a trim actuator to adjust the trim position of the marine drive based on the trim position instruction, the steering position, and the allowable steering angle range such that the steering position of the marine drive remains within the allowable steering angle range for the adjusted trim position.

Claims

1. A method of controlling a marine drive on a marine vessel, the method comprising: receiving a trim position instruction to adjust a trim position of the marine drive; receiving a steering position of the marine drive; determining an allowable steering angle range based on the trim position instruction and/or the adjusted trim position of the marine drive; and controlling a trim actuator to adjust the trim position of the marine drive based on the trim position instruction, the steering position, and the allowable steering angle range such that the steering position of the marine drive remains within the allowable steering angle range for the adjusted trim position.

2. The method of claim 1, wherein the steering angle range is configured to avoid collision between adjacent marine drives on the marine vessel when effectuating the trim position adjustment.

3. The method of claim 1, further comprising: receiving a steering position of an adjacent marine drive; and controlling the trim actuator to adjust the trim position of the marine drive based further on the steering position of the adjacent marine drive.

4. The method of claim 3, wherein the trim actuator is controlled to adjust the trim position of the marine drive so that the steering position of the adjacent marine drive remains within the allowable steering angle range for the respective trim position.

5. The method of claim 1, wherein the allowable steering angle range narrows around a centered steering position as the trim position is adjusted toward a maximum trim position.

6. The method of claim 1, wherein the allowable steering range is a maximum steering angle range for trim positions below a threshold trim position.

7. The method of claim 6, wherein the allowable steering range is a minimum steering angle range for trim positions above the threshold trim position.

8. The method of claim 6, wherein the allowable steering angle range progressively narrows around a centered steering position as the trim position is adjusted above the threshold trim position and toward a maximum trim position.

9. The method of claim 8, wherein at the threshold trim position a propeller on the marine drive is at or above a water surface.

10. The method of claim 1, wherein the trim position instruction adjusts the trim position to a target trim position, and further comprising: determining the allowable steering angle range for the target trim position; and only adjusting the trim position of the marine drive to the target trim position if the steering position of the marine drive is within the allowable steering angle range for the target trim position.

11. The method of claim 10, further comprising only adjusting the trim position of the marine drive to the target trim position if a steering position of each adjacent marine drive is also within the allowable steering angle range for the target trim position.

12. A system for controlling position of a marine drive on a marine vessel, the system comprising: a user input device operable by a user to input a trim position instruction to adjust a trim position of the marine drive; a trim actuator configured to adjust a trim position of the marine drive in response to the trim position instruction; a steering actuator configured to adjust a steering position of the marine drive; a control system configured to: receive the trim position instruction; determine an allowable steering angle range based on the trim position instruction; receive a steering position of the marine drive; and control a trim actuator to adjust the trim position of the marine drive based on the trim position instruction, the steering position, and the allowable steering angle range such that the steering position of the marine drive remains within the allowable steering angle range for the adjusted trim position.

13. The system of claim 12, wherein the steering angle range is configured to avoid collision between adjacent marine drives on the marine vessel when effectuating the trim position adjustment.

14. The system of claim 12, wherein the control system is further configured to: receive a steering position of an adjacent marine drive; and control the trim actuator to adjust the trim position of the marine drive based further on the steering position of the adjacent marine drive.

15. The system of claim 14, wherein the trim actuator is controlled to adjust the trim position of the marine drive so that the steering position of the adjacent marine drive remains within the allowable steering angle range for the respective trim position.

16. The system of claim 12, wherein the control system is further configured to narrow the allowable steering angle range around a centered steering position as the trim position is adjusted toward a maximum trim position.

17. The system of claim 12, wherein the allowable steering range is a maximum steering angle range for trim positions below a threshold trim position.

18. The system of claim 12, wherein the trim position instruction adjusts the trim position to a target trim position, and wherein the control system is further configured to: determine the allowable steering angle range for the target trim position; and only adjust the trim position of the marine drive to the target trim position if the steering position of the marine drive is within the allowable steering angle range for the target trim position.

19. The system of claim 18, further comprising only adjusting the trim position of the marine drive to the target trim position if a steering position of each adjacent marine drive is also within the allowable steering angle range for the target trim position.

20. A propulsion system for a marine vessel, the system comprising: a plurality of marine drives configured to propel a marine vessel; a user input device operable by a user to input a trim position instruction to adjust a trim position of one or more of the marine drives; a trim actuator for each marine drive configured to adjust a trim position of the respective marine drive in response to the trim position instruction; a steering actuator for each marine drive configured to adjust a steering position of the respective marine drive; and a control system configured to control the trim position adjustment of each of the plurality of marine drives based on the steering position of the respective marine drive to avoid collision between adjacent marine drives on the marine vessel when effectuating the trim position adjustment.

21. The system of claim 20, wherein the control system is configured to control the trim position of each of the plurality of marine drives based on whether the steering position of the respective marine drive is within an allowable steering angle range.

22. The system of claim 21, wherein the allowable steering angle range is a range of steering angles for the respective marine drive determined based on the trim position instruction and/or an adjusted trim position of the respective marine drive.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure is described with reference to the following Figures.

(2) FIG. 1 is a schematic depiction of a marine vessel having a plurality of marine drives and user input devices.

(3) FIG. 2 is a side view of a marine vessel having a marine drive in a neutral trim position.

(4) FIG. 3 is a side view of a marine vessel having a marine drive in a trimmed down position.

(5) FIG. 4 is a side view of a marine vessel having a marine drive in a trimmed up position.

(6) FIG. 5 is a side view of a marine vessel having a marine drive in a maximum trim position where the drive is fully trimmed up.

(7) FIG. 6 is a schematic showing an exemplary a control system for controlling a plurality of marine drives according to one embodiment of the present disclosure.

(8) FIGS. 7 and 8 are graphs showing exemplary relationships between trim and steering angle range, exemplifying embodiments of the present disclosure.

(9) FIGS. 9 and 10 are flow charts illustrating exemplary methods of controlling position of marine propulsion devices.

DETAILED DESCRIPTION

(10) The inventors have recognized that a problem exists with drive collision where, in marine vessels with multiple independently steerable drives (e.g., multiple outboard drives configured for joystick steering), the drives can collide with one another at certain steering and trim positions. The chance for drive collision becomes greater when the drives are mounted close together, such as where several drives are mounted to the transom or where two or more drives are mounted close together at the center of the vessel's stern. Drive collision can damage the propeller, gear case, or other portions of either or both of the colliding drives, and can even leave one or more of the colliding drives inoperable. Thus, avoidance of drive collision is extremely important.

(11) On many current multi-engine vessels, drive collision is avoided by utilizing a mechanical tie bar (such as a collapsible tie bar) or other mechanical link between the drives that prevents the drives from being steered into positions where they might collide with peer drives. These tie bar solutions connect adjacent drives together in such a way so as to physically prevent adjacent drives from moving into positions where they can collide with one another. However, tie bar solutions and other solutions that mechanically link two drives are not workable for drive configurations where the steerable potion of the drive is below the water surface, such as stern drives and or outboard drives with steerable gear cases. In these types of drives, a tie bar or other mechanical link between the steerable drive portions would have to be mounted below the water surface, which would create drag and other unwanted affects and would not be a workable solution. Thus, a solution is needed for preventing drive collision that does not require mechanically linking the marine drives.

(12) Moreover, through their experimentation, research, and experience in the relevant field, the inventors have recognized that drive collision is most likely to happen during trim transition, where the trim angle of one or more of the drives is being adjusted. The risk of drive collision is particularly high during large trim adjustments where one drive is being fully trimmed up to pull it out of the water or is being trimmed down from a fully trimmed up position to put the drive into the water. During these trim transitions, a situation can occur where the steerable portion of the trimmed drive (e.g., that that includes the propeller) impacts a portion of the adjacent drive, such as the cowl, gearcase, cavitation plate, etc. Alternatively, a situation can occur where the gearcase or other portion of the trimmed drive can be lowered onto and impact the propeller or steerable portion of the adjacent drive. These types of impacts can cause severe damage to one or both colliding drives.

(13) In view of the forgoing problems and challenges with drive collision avoidance recognized by the inventors, the disclosed system and method were developed to provide a software solution for avoiding drive collision. In the disclosed system and method, the allowable steering angle range of one or more of the marine drives is limited based on trim position. For example, an allowable steering angle range is defined for various trim positions. The drive steering angle is then automatically controlled to remain within the allowable steering angle range as the drive is trimmed up or trimmed down in response to an instruction to change the trim position of the drive.

(14) In one embodiment, trim position and steering position are adjusted simultaneously so as to force the steerable drive toward a centered steering position as the trim position increases toward a maximum trim position. In certain embodiments, a threshold trim position is set below which a maximum steering angle range is permitted, and thus no limitations are set beyond the normal steering angle limitations set for a multi-drive system. Once the trim position is adjusted above the threshold trim position, the allowable steering angle range narrows around the centered steering position so as to force the marine drive toward the centered position, particularly once the drive has reached a threshold trim position where the propeller is substantially or totally above the water surface. Thereby, the drives are prevented from moving into positions where they can collide with peers because no collision will occur when the drives are in or near the centered steering position.

(15) FIG. 1 schematically depicts a marine vessel 10 having a plurality of marine drives 12a, 12b. In the example, the marine drives 12a, 12b are port and starboard marine drives respectively, and are shown coupled to the stern of the marine vessel 10. In other embodiments, the marine vessel 10 may be configured with more than two drives, such as multi-drive systems with three, four, five, or six drives. The marine drives 12a, 12b shown herein are outboard motors, but could alternatively be stern drives. The marine vessel 10 further comprises at least one user input device. In the example shown, the at least one user input device comprises a steering wheel 14, throttle lever 16, joystick 18, keypad 20, touchscreen 22, and/or trim control buttons 23. The trim control buttons 23 may be a keypad, lever, or any other arrangement configured to facilitate user input to control trim position of the marine drives 12. In other embodiments, the keypad 20 and/or touchscreen 22 may be configured as user input devices for inputting a trim position instruction to control and adjust trim position of one or more of the marine drives 12. Each of these user input devices is located at a helm 24 of the marine vessel 10.

(16) Each of the user input devices 14, 16, 18, 20, 22 is communicatively connected via a controller area network (CAN) bus 26 to one or more controllers, such as command control modules (CCMs) 28a, 28b. The CCMs 28a, 28b effectively receive and send all signals from and to the user input devices at the helm 24. In the depicted examples, the CCMs 28a, 28b are communicatively connected via the CAN bus 26 to engine control modules (ECMs) 30a, 30b on each marine drive 12. This control system 32 arrangement is merely representative and various other arrangements are known and within the scope of the disclosure. For example, each drive may comprise two or more controllers, such as a powertrain control module (PCM) and a thrust vector module (TVM), as is well-known in the art. In other alternative control system 32 arrangements, a central control module may be provided in addition to or in place of the CCMs 28a, 28b.

(17) The system 9 for positioning a marine drives 12a and 12b further includes a trim actuator 48a and 48b and a steering actuator 50a and 50b associated with each drive 12a and 12b. In the depicted example, each CCM 28a and 28b is communicatively connected (e.g., via a CAN bus arrangement) and configured to control the trim actuators 48 and steering actuators 50; however, various other control arrangements are possible and well known in the relevant art. The trim actuators 48a, 48b move the marine drives 12a, 12b to a requested trim position, in response to signals sent from the CCMs 28a, 28b, such as based on input from the user input devices (e.g., trim control buttons 23). Further, the control system 32 comprises trim angle sensors 35a, 35b for sensing current trim positions of the marine drives 12a, 12b and providing this data to the control modules via the CAN bus 26. The steering actuators 50a, 50b steer the marine drives 12a, 12b in response to signals sent from the CCMs 28a, 28b via the CAN bus 26. Control of the steering actuators 50a and 50b may further be based on steering position sensed by the steering position sensors 55a and 55b configured to sense and actual steering position of the steerable drive portion.

(18) Now referring to FIGS. 2-5, various trim positions of the marine drives 12a, 12b will be described. In the example shown in FIGS. 2-5, only the starboard marine drive 12b is shown. However, it should be understood that the port marine drive 12a is or may be positioned in the same trim positions as the starboard marine drive 12b shown in these figures, and can therefore not be seen behind the starboard marine drive 12b. It should be understood that in alternative embodiments, the marine vessel 10 may be propelled by more than two marine drives. It should also be understood that in other examples, the two marine drives 12a, 12b may have different trim positions from one another.

(19) In each of FIGS. 2-5 the trim position of the marine drive 12b is shown with respect to a dashed line representing a vertical axis 34. Additionally, another dashed line in each of the figures represents a longitudinal axis 36 through the marine drive 12b. The angle between the vertical axis 34 and the longitudinal axis 36 is the trim angle A. In FIG. 2, the marine drive 12b is in a neutral trim position in which the vertical axis 34 and the longitudinal axis 36 are generally parallel to one another. In FIG. 3, the marine drive 12b is trimmed all the way down (trimmed in) such that a propeller 42 of the marine drive 12b is closer to a hull 38 of the marine vessel 10 than when the marine drive 12b is in the neutral trim position. This position is sometimes referred to as “full tuck.” In FIG. 4 the marine drive 12b is trimmed up (trimmed out) such that the propeller 42 is further from the hull 38.

(20) In FIG. 4 the propeller 42 of the drive 12b is at or near the water surface. For trim positions at and/or above that point, thrust will not be fully effectuated because the propeller 42 will not be fully engaged with the water. Thus, the drive 12b will to be able to fully effectuate steering or thrust commands in that position and trim positions at or above that point are generally undesirable when the drive 12b is engaged propulsion operations for the vessel. FIG. 5 is a closer depiction of the drive 12b trimmed up even further, which may represent the drive 12b in a maximum trim position where it is fully trimmed up (or trimmed out) and is lifted out of the water. Marine drives are placed in this position when they are inoperative, such as when they are not needed for low speed steering operations or when a malfunction has occurred with that drive. In this position the drive 12b is lifted out of the water so that it does not create drag and/or so that it is out of the way.

(21) FIG. 2 depicts the marine drive 12b in a neutral trim position. In the example shown in FIG. 2, the trim angle of the marine drive 12b is such that a reverse thrust R provided by the marine drive 12b does not intersect with the hull 38 of the marine vessel 10 during any rotational orientation of the marine drive 12b about its longitudinal axis 36. Further, the trim angle of the marine drive 12b is such that reverse thrust R is not trimmed too far up away from the vertical axis 34 such that the marine drive 12b may still efficiently achieve reverse or rotational movement of the marine vessel 10. In the example of FIG. 2, the trim position (shown by longitudinal axis 36) is substantially parallel to the vertical axis 34.

(22) The marine drive 12b can be acutely or obtusely angled with respect to the vertical axis 34. FIG. 3 shows the marine drive 12b in a trimmed down (trimmed in) position. In the fully trimmed in position, the marine drive 12b is angled such that the propeller 42 is closer to the hull 38 of the marine vessel 10 than when in the neutral position, and its longitudinal axis 36 is oriented at an angle A1 with respect to the vertical axis 34 (which may be described as a negative angle).

(23) In FIG. 4, the marine drive 12b is shown in a trimmed up (trimmed out) position in which the propeller 42 is further from the hull 38 of the marine vessel 10 than when in the neutral position, and the longitudinal axis 36 extends at an angle A2 with respect to the vertical axis 34. This provides a reverse thrust R in a somewhat downwardly angled direction as shown and minimal or no forward thrust can be provided because the propeller 42 is at or above the water surface; however, when the vessel 10 is on plane this drive position may be operable to provide forward thrust. In positions beyond that in FIG. 4, such as the maximally trimmed up position at FIG. 5, no thrust can be effectuated. To provide just one example, the angle A2 may be around 20 degrees of trim, which in various embodiments may be greater or less depending on the vessel configuration, drive configuration, etc.

(24) The trimmed down position shown in FIG. 3 is a position that is conventionally used during initial forward acceleration (or launch) of the marine vessel 10 until full forward translation when the marine vessel 10 is on-plane. During such initial forward acceleration, the propeller 42 rotates forwardly to provide forward thrust (shown by dashed line F) to propel the marine vessel 10 forwardly. When the marine drive 12b is at this trim position for accelerating into forward translation of the marine vessel 10, the marine drive 12b provides forward thrust F that is angled somewhat downwardly.

(25) Once the marine vessel 10 is in full forward translation and on-plane, the marine drive 12b is typically trimmed back out of the trim position shown in FIG. 3, past the vertical axis 34, and to a slightly raised (trimmed out) trim position. (e.g., toward the position in FIG. 4). This trimmed up position achieves, for example, optimal speed, riding vessel angle, fuel economy, and/or other desired performance characteristics.

(26) FIG. 6 depicts a schematic representation of a control system 32 that can be used to position the marine drives 12a, 12b on the marine vessel 10. As described hereinabove, the control system 32 comprises a throttle lever 16, joystick 18, keypad 20, trim input 23 (e.g., trim control buttons), and steering wheel 14 (collectively, the user input devices) connected via a CAN bus 26 to CCMs 28a, 28b. It should be understood by those having skill in the art that a CAN bus need not be provided, and that these devices could instead be wirelessly connected (or connected by a different communication system) to one another and/or to the CCMs 28a, 28b. Further, the connections shown in dashed lines in both FIGS. 1 and 6 are for exemplary purposes only, and may be wired other than as shown herein.

(27) Signals from each of the user input devices 14, 16, 18, 20, 23 are sent via the CAN bus 26 to helm controller(s) (in this example CCMs 28a, 28b), which interpret these signals and send commands to the trim actuators 48a and 48b and steering actuators 50a and 50b. In the example shown, the CCMs, PCMs, and TVMs are illustrated as separate modules controlling separate functions aboard the marine vessel 10; however, it should be understood that any of the control sections shown and described herein could be provided in fewer modules or more modules than those shown.

(28) Any of the controllers may have a memory and a programmable processor, such as processor 37 and memory 33 in CCM 28a. As is conventional, the processor 37 can be communicatively connected to a computer readable medium that includes volatile or nonvolatile memory upon which computer readable code (software) is stored. The processor 37 can access the computer readable code on the computer readable medium, and upon executing the code can send signals to carry out functions according to the methods described herein below. Execution of the code allows the control system 32 to control a series of actuators (for example steering actuators 50a, 50b and trim actuators 48a, 48b) of the marine drives 12a, 12b. Processor 37 can be implemented within a single device but can also be distributed across multiple processing devices or sub-systems that cooperate in executing program instructions. Examples include general purpose central processing units, application specific processors, and logic devices, as well as any other type of processing device, combinations of processing devices, and/or variations thereof. The control system 32 may also obtain data from sensors aboard the vessel (e.g., trim position sensors 35a and 35b and steering position sensors 55a and 55b, and the processor 37 may save or interpret the data as described herein below. In the example shown, at least the port CCM 28a comprises a memory 33 (such as, for example, RAM or ROM), although the other control modules could be provided with a memory as well.

(29) Now referring to FIGS. 7-10, exemplary methods for positioning the marine drive 12a, 12b on the marine vessel 10 are described and shown. FIGS. 7 and 8 are graphs illustrating various schemes for setting an allowable steering angle range based on trim. The allowable steering angle range represents the permitted steering angles, and thus the angles at which the drive can be positioned in response to a steering instruction. The allowable steering angles may be symmetrical about the centered steering position, or 0 steering angle, which is generally perpendicular to the stern of the vessel 10. The graphs represent allowable steering angle magnitude from the centered steering position, and thus the allowable steering angle range will be the depicted steering angle magnitude on either side of the centered steering position. For instance, the maximum allowed steering angle of 30 degrees represents an allowable steering angle range of +30 degrees and −30 degrees with respect to the centered steering position. When the allowable steering angle range is set to the maximum steering range, the drive can be steered to any position within that range 60 degree total range, such as based on inputs from the steering wheel 14, joystick 18, etc.

(30) The allowable steering angle range is a maximum steering angle range where no additional constraints are placed on the permitted steering angles beyond those normally in place for steering the drives on the marine vessel. As will be known to a person of ordinary skill in the art, the maximum steering angle range is normally constrained in drive-by-wire applications, for example, based on the range of the steering actuator 50, the mount for the steerable portion of the marine drive 12, the location and arrangement of the marine drives, etc. At the maximum steering angle range, no trim-based constraints are enacted. But as the trim angle increases toward the maximum trim angle, the allowable steering angle range narrows around the centered steering position so as to force the marine drive toward the centered steering position as the marine drive is trimmed up toward the maximum trim position. This may be a gradual centering as the drive is trimmed up. In other embodiments, the drive may be automatically and fully centered when it is raised above a threshold trim position.

(31) Various algorithms and relationships for controlling steering position based on trim may be implemented, examples of which are shown in FIGS. 7 and 8. FIG. 7 depicts three different exemplary relationship between trim angle and allowable steering angle range. In these examples, the allowed steering angle range progressively narrows around the centered steering position, between a maximum steering angle range at a minimum trim position and a zero steering angle (representing a centered steering position) at a maximum trim position where the marine drive is fully trimmed up and out of the water. In these examples, the minimum trim position is a steering angle of −3 degrees and the maximum steering angle is 90 degrees. As will be known to a person having ordinary skill in the art, the values and range between minimum and maximum steering angles may vary depending on the vessel and drive configurations.

(32) Line 72 represents an exponential relationship between allowed steering angle and trim angle where the allowable steering angle range decreases exponentially as the trim angle increases. In the depicted exponential relationship, the allowable steering angle range is at a maximum at low trim angle ranges close to 0, and begins to narrow at about 5 degrees of trim. In other embodiments, the allowable steering angle range may remain at the maximum steering angle range for trim positions below a threshold trim position, such as below the first trim position threshold 81 illustrated with respect to the modified linear funnel illustrated a lines 76 and discussed below. The exponential relationship is configured to progressively move the steerable drive to the centered steering position as the trim angle of the drive increases such that the centered steering position is reached at or before the drive reaches the maximum trim position. In the depicted embodiment, the steering angle constraints are configured such that the drive is forced to the centered position as the trim angle reaches a second threshold trim position 82, which is less than the maximum trim position.

(33) The two other lines at FIG. 7 depict exemplary linear relationships between allowed steering angle range and trim angle. Line 74 represents a linear funnel where the allowed steering angle range decreases linearly as the trim angle increases between the minimum trim position where the drive is fully tucked and the second threshold where the drive is at or near the maximum trim position. Line 76 represents a second exemplary linear relationship where the steering angle range decreases linearly between a first threshold trim position 81 and the second threshold trim position 82. Thus, the allowable steering angle range is the maximum steering angle range of 30 degrees at all trim positions below the threshold trim position 81, which in the depicted example is about 15 degrees of trim. The allowable steering angle range then progressively narrows as the trim angle increase so as to force the drive into the centered position.

(34) FIG. 8 represents another embodiment where the relationship between trim and steering angle is a step function. An exemplary step profile is presented by line 78, where a maximum allowable steering angle range is associated with trim positions below the threshold trim position 83 and for trim positions above the threshold trim position 83, the allowable steering angle range is the centered steering position. Thus, the steerable drive 12 is centered once during the trim up process when the trim angle passes the threshold 83. This arrangement has the benefit of only needing to activate the steering actuator 50 once during a trim up routine where the drive is being raised out of the water. In certain embodiments, hysteresis may be implemented to avoid toggling the steering position of the drive if trim is adjusted slightly up or down around the established threshold trim value.

(35) In the example depicted at FIG. 8, the threshold trim position 83 is 30 degrees; however, in various embodiments the threshold trim position can be less than or greater than 30 degrees. Preferably, at the threshold trim position 83 the propeller 42 is at or above the water surface, and thus the drive is not actively steering the marine vessel. Thus, a forced change in steering position will not affect the propulsion vector acted on the marine vessel 10. For example, the threshold trim position 83 may be greater than or equal to the trimmed out position depicted a FIG. 4 where the propeller 42 is at the water surface. In other embodiments, the threshold trim position 83 may be substantially greater than the angle depicted at FIG. 4 such that the propeller is well above the water surface before the centering occurs.

(36) The allowable steering angle range is then determined based on trim positions. For example, the relevant controller may store a lookup table providing allowable steering angle range in association with trim angle. The allowable steering angle range may then be determined by utilizing the lookup table, such as based on a current steering angle occupied by the marine drive and sensed by the trim angle sensor 35 or based on a target trim position determined based on the trim position instruction provided at the user input device.

(37) FIGS. 9 and 10 depict exemplary methods of controlling a marine drive on a marine vessel in order to avoid drive collision during trim position changes, as described herein. In the flowchart at FIG. 9, the method 100 includes receiving a trim position instruction at step 102, such as from a user input device configured to receive user input to adjust a trim position of the marine drive (e.g., trim control input buttons 23, or any other user input device configured for inputting trim control commands). An allowable steering range is then determined at step 104 that accounts for the adjusted trim position based on the trim position instructions. The trim position and steering position are then adjusted accordingly at step 106 such that the steering angle of the steerable marine drive remains within the allowable steering angle range. In various embodiments, the allowable steering angle range may be determined based on a trim position occupied by the drive, such as after effectuating the trim position adjustment commanded by the trim position instruction. In other embodiments, the allowable steering angle range may be determined based on the target trim position commanded by the trim position instruction. An example of such an embodiment is depicted at FIG. 10.

(38) In the flowchart at FIG. 10, the method 100 of controlling a marine drive includes receiving a trim position instruction at step 110 and then determining a target trim position at step 112 based on the trim position instruction. Target trim position determinations based on user inputs at trim control input devices are well known in the relevant art, examples of which are shown and described in U.S. Pat. No. 9,751,605, which is incorporated herein. Logic is executed at step 114 to determine whether the target trim position is greater than a threshold trim position. The target trim position here is a threshold, wherein at trim positions below the threshold steering range is not narrowed based on trim. Thus, if the target trim position is less than the threshold trim position, then no steering adjustment is made as represented at step 115.

(39) In embodiments where the relationship between trim and steering position is a step function, such as exemplified in FIG. 8, the threshold trim position utilized at step 114 may be the threshold trim position 83 representing a position where the propeller 42 of the marine drive is at or above the water surface. However, in various embodiments the threshold trim position utilized at step 114 may be at a lower trim position, such as the threshold trim position 81 represented at FIG. 7.

(40) Once the target trim position exceeds the threshold trim position, the allowable steering angle range is narrowed at step 116 based on the target trim position. For example, the allowable steering angle range may be determined using a lookup table based on the target trim position. In embodiments where the allowable steering angle range is a step function such as that depicted in FIG. 8, the allowable steering angle range will represent the centered steering position. The steering actuator is then controlled at step 118 to maintain the steering position within the allowable steering angle range. The trim actuator is controlled to adjust the position of the marine drive to the target trim position at step 120.

(41) This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. 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. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have features or structural elements that do not differ from the literal language of the claims, or if they include equivalent features or structural elements with insubstantial differences from the literal languages of the claims.