Controller and method for controlling a drive motor of a product conveyor belt at a checkout

Abstract

A controller for a drive motor (60) of a product conveyor belt at a checkout has a phase-start cutting and/or phase-end cutting controller (50) that controls the drive motor (60) in such a manner that the product conveyor belt is accelerated with reduced torque from a non-driven state. A start controller controls the drive motor (60) in such a manner that the drive motor (60) initially drives with a non-reduced torque when accelerating the product conveyor belt from the non-driven state before the phase-start cutting and/or phase-end cutting controller (50) further accelerates the product conveyor belt with reduced torque.

Claims

1. A controller for a drive motor (60) of a product conveyor belt at a checkout comprising: a phase-start cutting and/or phase-end cutting controller (50) that controls the drive motor (60) such that the product conveyor belt is driven with a reduced torque starting from a non-driven state, and a start controller that controls the drive motor (60) in such a manner that the drive motor (60) initially drives with a non-reduced torque when accelerating the product conveyor belt from the non-driven state before the phase-start cutting and/or phase-end cutting controller (50) further accelerates the product conveyor belt with reduced torque.

2. The controller of claim 1, wherein the start controller is configured such that the drive motor (60) drives the product conveyor belt with non-reduced torque for a set time period before the phase-start cutting and/or phase-end cutting controller (50) further accelerates the product conveyor belt with reduced torque.

3. The controller of claim 1, wherein the start controller is configured such that the product conveyor belt is driven with the non-reduced torque until a full load current is reached when driving the product conveyor belt.

4. The controller claim 1, wherein the phase-start cutting and/or phase-end cutting controller (50) increases the torque of the drive motor substantially continuously and/or linearly up to the full torque when accelerating the product conveyor belt.

5. The controller of claim 1, wherein the phase-start cutting and/or phase-end cutting controller (50) increases the drive motor torque beginning at a predetermined ramp starting torque (MRS) that corresponds to about 10% to about 50% of an operating torque (MB) up to the full operating torque (MB) when accelerating the product conveyor belt.

6. The controller of claim 1, wherein the start controller is configured such that after a stoppage of the product conveyor belt, a dead time (TT) of a predetermined duration is provided, after the expiration of which the product conveyor belt is re-accelerated as soon as possible.

7. The control of claim 1, wherein the phase-start cutting and/or phase-end cutting controller (50) continues to control the drive motor (60) such that the product conveyor belt is braked from a driven state with an initially reduced torque before the drive motor (60) stops driving the product conveyor belt.

8. The controller of claim 1, with a trigger (40) for initiating the acceleration of the product conveyor belt from the non-driven state, and/or for initiating a stoppage of the product conveyor belt from a driven state.

9. A control unit (80) for a checkout system that has: a product conveyor belt, a drive motor (60), and a phase-start cutting and/or phase-end cutting controller (50) that controls the drive motor (60) such that the product conveyor belt is driven with a reduced torque starting from a non-driven state, the control unit (80) comprising: a start controller that controls the drive motor (60) in such a manner that the drive motor (60) initially drives with a non-reduced torque when accelerating the product conveyor belt from the non-driven state before the phase-start cutting and/or phase-end cutting controller (50) further accelerates the product conveyor belt with the reduced torque, wherein the control unit (80) is configured as a separate component that has the start controller and is connected between the phase-start cutting and/or phase-end cutting controller (50) on the one hand in the drive motor (60) on the other hand.

10. The control unit (80) of claim 9, with its own power connection (83) that is configured separately from a power connection for the phase-start cutting and/or phase-end cutting controller (50).

11. The control unit (80) of claim 9 with its own internal phase-start cutting and/or phase-end cutting controller that further accelerates the product conveyor belt with reduced torque instead of the phase-start cutting and/or phase-end cutting controller (50) of the checkout system after the start controller drives the product conveyor belt with initially non-reduced torque when accelerating the product conveyor belt from the non-driven state.

12. A control unit (80) for a checkout system that has: a product conveyor belt, a drive motor (60) and a trigger (40) for initiating the acceleration of the product conveyor belt from the non-driven state, and/or for initiating a stoppage of the product conveyor belt from a driven state; comprising: a phase-start cutting and/or phase-end cutting controller (50) that controls the drive motor (60) such that the product conveyor belt is driven with a reduced torque starting from a non-driven state, and a start controller that controls the drive motor (60) in such a manner that the drive motor (60) initially drives with a non-reduced torque when accelerating the product conveyor belt from the non-driven state before the phase-start cutting and/or phase and cutting controller (50) further accelerates the product conveyor belt with reduced torque, wherein the control unit (80) is configured as a separate component that has the start controller and the phase-start cutting and/or phase-end cutting controller as an internal component, and is connected between the trigger (40) and the drive motor (60).

13. The control unit (80) of claim 9, wherein the control unit (80) is connected to a plurality of drive motors (60) of different product conveyor belts and is configured to control this plurality of drive motors (60) with the at least one starting controller.

14. The control unit (80) of claim 9 further comprising an interface for: undertaking software updates for the control unit (80); for reading out parameters and/or data from the control unit (80); and/or for establishing a connection to a module of the checkout system.

15. The control unit (80) of claim 9 with a thermal switch for overload protection of the drive motor (60).

16. The control unit (80) of claim 9 further comprising a memory module for saving data from the control unit.

17. The control unit (80) of claim 16, further comprising: a forecasting module that is configured to derive and/or estimate a forecast characteristic value for a residual life of the drive motor (60) from the saved data of the control unit, and/or a usage profile module which is configured to derive and/or estimate a usage profile relating to the utilization of the checkout system from the saved data.

18. A checkout system comprising: a product conveyor belt, a drive motor (60) and the controller of claim 1.

19. A checkout system comprising: a product conveyor belt, a drive motor (60), a phase-start cutting and/or phase-end cutting controller (50) that controls the drive motor (60) such that the product conveyor belt is driven with a reduced torque starting from a non-driven state, and further comprising the control unit (80) of claim 9.

20. A method for controlling a drive motor (60) of a product conveyor belt at a checkout, wherein when accelerating the product conveyor belt from a non-driven state, initially, the method comprising: controlling the drive motor (60) such that the drive motor (60) drives the product conveyor belt with non-reduced torque before controlling a phase-start cutting and/or phase-end cutting controller (50) to control the drive motor (60) such that the product conveyor belt is accelerated further with a reduced torque.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a diagram of the operation of a phase-end cutting control.

(2) FIG. 2 shows a diagram of a typical current characteristic for a drive motor of a product conveyor belt.

(3) FIG. 3 shows a diagram of a typical current characteristic for a drive motor of a product conveyor belt together with a characteristic of power that is applied to the drive motor according to the invention.

(4) FIG. 4 shows a schematic representation of a controller according to the invention of a drive motor of a product conveyor belt with a phase-start cutting and/or phase-end cutting controller.

(5) FIG. 5A shows a schematic representation of a conventional controller of a drive motor of a product conveyor belt.

(6) FIG. 5B shows a schematic representation of a controller of a drive motor of a product conveyor belt that is retrofitted with a control unit according to the invention.

(7) FIG. 6 shows a diagram of the controlled torque according to an exemplary embodiment over several start/stop cycles.

DETAILED DESCRIPTION

(8) FIG. 1 shows a diagram of the operation of a phase-end cutting controller. The diagram shows the voltage characteristic of an AC voltage that is approximately sinusoidal plotted over time. The voltage can for example be a typical AC voltage that is provided by for example a single-phase power grid. In order to effectuate a gentle startup of a product conveyor belt, a phase controller cuts a start-portion, or respectively end-portion, of the phase of the shown voltage to accelerate a product conveyor belt. The phase controller also hence actually applies the AC voltage to a drive motor of a product conveyor belt only for parts of the phases.

(9) Given a period T, voltage could be applied to the drive motor from point in time 0 to point in time T/2 during a first sign wave of the AC voltage portrayed in the diagram that is shown directly adjacent to the zero point in time in the diagram. During this time period, the phase-end cutting controller cuts this voltage for the majority of the time between 0 and T/2 and only applies the voltage to the drive motor toward the end of the shown first sign wave.

(10) In the shown diagram, the periods in which the phase-end cutting controller applies a voltage to the drive motor of, for example, a product conveyor belt is marked by a hatched area between the sinusoidal voltage and the zero axis of the voltage. If said area is unfilled, i.e., portrayed white, the phase-end cutting controller cuts the voltage, i.e., does not apply the voltage to the drive motor.

(11) During the first, positive sinusoidal voltage arc (i.e., within the time period from 0 to T/2), the phase-end cutting controller only lets the voltage through during about the last 15% of the associated period of T/2. This percentage slowly increases the AC voltage from sign wave to sign wave until the phase-end cutting controller has applied the entire phase voltage to the drive motor in the sign wave portrayed on the far right that is the seventh sign wave in the diagram. In this case it should be noted that the number of sign waves (or actually half sign waves) is to be understood as an example. In reality, the phase-end cutting controller regularly lets the full voltage through only at a substantially later point in time.

(12) In other words, the phase-end cutting controller applies the voltage to the drive motor only at certain phase angles cp. The phase-end cutting controller applies the voltage to the drive motor only beginning at a certain start phase angle up to the next zero crossing of the AC voltage. This start phase angle can for example change from zero crossing to zero crossing of the AC voltage so that the phase-end cutting controller always applies voltage to the drive motor earlier and earlier until the full voltage is applied to the drive motor. In general, a phase controller can be designed so that it applies voltage to the drive motor later and later during the acceleration period T of the AC voltage until it applies the full voltage.

(13) The operation of a phase-start cutting controller is similar to that of a phase-end cutting controller. A difference between these two-phase controllers is that one cuts off the beginning of a sine wave, whereas the other cuts off the end of the sine wave. Otherwise, the two-phase controllers, i.e., the phase-start cutting controller and the phase-end cutting controller, have a similar effect. While the one phase controller applies voltage to the drive motor beginning at a start phase angle up to the zero crossing, the other only applies voltage from a zero crossing to an end phase angle. Since the principle of a phase-start cutting and/or phase-end cutting controller is well-known to a person skilled in the art, the operation of a phase-start cutting and phase-end cutting controller will not be addressed further at this juncture; instead, reference is made in this regard to the relevant professional literature.

(14) FIG. 2 shows a diagram of a typical current characteristic S for a drive motor of a product conveyor belt over time. Starting at a certain point in time that is portrayed in the diagram as point in time t.sub.v, the drive motor is driven under full load current. Before point in time t.sub.v, initially a start-up current is to be applied that moves the drive motor and the product conveyor belt out of a non-driven state. In this non-driven state, the product conveyor belt is in a resting state in which it does not move.

(15) In order for example to overcome the inertia of the product conveyor belt, initially the start-up current is to be applied that is configured to be many times greater than the full load current applied later. In the exemplary embodiment shown in FIG. 2, the start-up current is initially about six times as large as the full load current. Since the start-up current is regularly configured to be significantly greater than the full load current, starting a product conveyor belt by means of a drive motor that is controlled by a phase-start cutting or phase-end cutting controller can cause a jerky and sudden start of the product conveyor belt. This is because the slight torque applied to the drive motor during the first sign wave (see FIG. 1) cannot provide the high start-up current. This causes the product conveyor belt to initially not move before it starts with a jerk.

(16) The phase-end cutting shown in FIG. 1 causes the torque with which the drive motor drives the product conveyor belt to be initially low and only increase over time. This increase can for example be gradual and/or substantially linear depending on the change in the phase-start cutting by the phase-start cutting, or respectively phase-end cutting controller. The initially very slight torque is insufficient in this case to provide the high start-up current as shown in FIG. 2.

(17) FIG. 3 shows a diagram of a typical current characteristic S for a drive motor of a product conveyor belt together with a percentage of power that is applied to the drive motor according to the invention. The characteristic of the applied power is identified by P in FIG. 3. According to the invention, about 100% of the power P and accordingly about 100% of the torque can be applied, i.e., about 100% of the phase can be let through until the start-up current has been overcome. In the shown exemplary embodiment, the full torque is accordingly applied to the product conveyor belt from starting time t=0 until the point in time t.sub.v at which the full load current is reached. Only starting at point in time t.sub.v does the phase-start cutting and/or phase-end cutting controller assume increasing the torque under a full load current until about 100% of the power P, i.e., about 100% of the torque and about 100% of the phase are applied.

(18) Theoretically, the characteristic shown in FIG. 3 of the applied power P and phase can be advantageous at which the full torque is applied to the drive motor up to precisely the point in time t.sub.v, i.e., precisely until the full load current is reached. In practice, the full, i.e., non-reduced torque can also be applied for a preset time period instead before the phase-start cutting and/or phase-end cutting controller further controls the applied voltage. Consequently, the characteristic of the applied power, phase and torque can deviate in practice from the power characteristic P shown in FIG. 3. Accordingly, the step-like reduction in the torque and/or the beginning of the ramp of the phase-end cutting controller can occur at a point in time that deviates somewhat from the point in time t.sub.v, i.e., at a preset period. When such a preset time period is used, sensors can be omitted that for example detect and/or monitor the motor current.

(19) In the diagram portrayed in FIG. 3, the characteristic of the power P that is identified with a solid line and is indicated in percent corresponds with the opening angle of the phase-start cutting and/or phase-end cutting controller, and/or corresponds thereto. In this case, 100% of the power corresponds to the full, i.e., non-reduced torque that is applied to the product conveyor belt without reducing the phase of the drive motor. To stop the drive motor, a single simple, e.g., linear ramp can be used.

(20) FIG. 4 shows a schematic representation of a controller of a drive motor 60 of a product conveyor belt with a phase-start cutting and/or phase-end cutting controller 50. The controller is portrayed simplified. An AC voltage source and/or current source 10 is connected to a rectifier 20 as well as to the phase-start cutting and/or phase-end cutting controller 50. The rectifier 20 converts the alternating current obtained from the current source 10 into direct current and thereby supplies a microcontroller 30. The microcontroller 30 receives a signal from a trigger 40 that for example can be configured as a sensor and/or as a foot pedal. From the trigger 40, both a start signal for starting a product conveyor belt out of a non-driven state as well as a stop signal for stopping the moving product conveyor belt can be sent to the microcontroller 30.

(21) The microcontroller 30 can exchange signals with the phase-start cutting and/or phase-end cutting controller 50. Accordingly, the microcontroller 30 can have a start controller that, after receiving a start signal from the trigger 40, communicates to the phase-start cutting and/or phase-end cutting controller 50 to initially apply the full torque to the drive motor 60 beginning with the phase-end cutting. In so doing, the microcontroller 30 can also control the set time period for which the full torque is applied to the drive motor 60.

(22) The phase-start cutting and/or phase-end cutting controller 50 is connected to the current source 10 whose phase it controls as shown in FIG. 1 such that the phase is cut at the start and/or end of the phase. The phase-start cutting and/or end cutting controller 50 is moreover connected to a drive motor 60, wherein the phase-start cutting and/or phase-end cutting controller 50 controls the torque such that the drive motor 60 is applied to a product conveyor belt at a checkout. The drive motor 60 can for example be configured as a single-phase asynchronous motor with a Steinmetz circuit that is arranged in a checkout system and/or checkout counter system with the produce conveyor belt as the conveyor belt. The use of a drive motor with a Steinmetz circuit has the advantage that special three-phase-current is unnecessary to drive the drive motor; instead, normal alternating current for example from the public power grid is suitable for driving.

(23) The alternating current source 10 can be configured as a typical 230 V/50 Hz AC voltage. The rectifier 20 can be configured as a power supply that converts the AC voltage supplied by the AC source 10 into a DC voltage which is used by the microcontroller 30. The microcontroller 30 can be configured as a module that starts and/or stops the phase-start cutting and/or phase-end cutting controller. The phase-start cutting and/or phase-end cutting controller 50 can have a TRIAC (short for triode for alternating current) as a switch, a zero crossing module for synchronizing the microcontroller 30 with the alternating voltage, and moreover electrical components for connecting an inductive load to the drive motor 60 in the shown exemplary embodiment.

(24) The trigger 40 signals to the microcontroller to start or stop the process.

(25) FIG. 5A shows a schematic representation of a conventional controller of a drive motor 60 of a product conveyor belt in a checkout system. The AC voltage source 10 feeds a control box 70 that receives a signal from the trigger 40 to start and stop the processor, i.e., to accelerate and stop a product conveyor belt. The control box 70 can have a phase-start cutting and/or phase-end cutting controller that, as described above, controls the energy and the torque with which the drive motor 60 drives the product conveyor belt.

(26) FIG. 5B shows a schematic representation of the controller shown in FIG. 5A that has an additional control unit 80. The control unit 80 is connected directly between the control box 70 and drive motor 60. For this, the control unit 80 has an input 82 by means of which it receives the signal from the control box 70 on when the product conveyor belt is to be started and/or stopped. The signal from the control box 70 is used by the control unit 80 only as a trigger signal, even if the control box 70 should have its own phase-start cutting phase-end cutting controller.

(27) The control unit 80 moreover has a motor output 81 by means of which the control unit 80 is connected to the drive motor 60. Via the motor output 81, the control unit 80 can control the amount of current and/or voltage with which to supply the drive motor 60. The torque is thereby controlled that the drive motor 60 applies to the product conveyor belt and with which it drives the product conveyor belt.

(28) The control unit 80 moreover has a power connection 83 by means of which the control unit 80 is connected by a power line 85 directly to the AC voltage source 10. The control unit 80 accordingly has its own additional power connection. In this case, the power line 85 circumvents the control box 70 and can be accordingly configured separately from the control box 70.

(29) The control unit 80 can have its own internal phase-start cutting and/or phase-end cutting controller as well as the above-described start controller with the microcontroller. The control unit 80 can be designed as a separate component with which the checkout system shown in FIG. 5A can be retrofitted.

(30) This provides a way of being able to retrofit checkout systems that are already installed and/or in use so that they can experience the advantages of the controller according to the invention.

(31) This provides an increase in the starting torque of an electric motor when using a phase-start cutting, or respectively phase-end cutting controller. The above-described controller can for example be used for electric motors, asynchronous AC motors, drum motors, belt drives and/or checkout counter systems. In this case, the drive motor is started gently by the controller without initially reducing the torque too strongly.

(32) In one embodiment, the control unit 80 is configured such that it functions even without the control box 70. In this embodiment, the control unit 80 completely replaces the control box 70, wherein it is connected directly between the AC voltage source 10, the trigger 40 and the drive motor 60. In this case, an additional controller can be omitted so that for example any control box 70 that may exist can be removed.

(33) FIG. 6 shows a diagram of the controlled torque M(t) according to an exemplary embodiment over several start/stop cycles. In this context, the time t is plotted on the x-axis, and the controlled torque from 0% to 100% of the maximum torque is plotted on the y-axis. In this case, the controlled torque M(t) shown in FIG. 6 on the y-axis does not precisely have to correspond to the actual torque applied at the respective point in time. More precisely, the phase angle and/or the opening angle of the corresponding motor controller controlled by the control box 70 and/or the control unit 80 is shown in percent on the y-axis in an exemplary embodiment for example of the opening angle of a TRIAC. If the product conveyor belt as provided according to an exemplary embodiment is operated with at least one asynchronous motor, the controlled phase angle does not necessarily have to correspond to the actually applied torque. Consequently, the diagram shown in FIG. 6 should rather be understood as a schematic sketch in which actually the controlled phase angle is shown on the y-axis that however corresponds to a controlled, desired and/or envisioned torque. The value shown as a percentage can also be termed the controlled torque M(t).

(34) In general, the term torque used in the context of this invention can also be understood as controlled torque, and/or as controlled phase angle. The same applies similarly to the terms operating torque, initial torque, and ramp start torque that can also be understood as controlled operating phase angle, controlled initial phase angle and controlled ramp start phase angle.

(35) The start points in time and stop points in time of the product conveyor belt are alternatingly identified below the time axis.

(36) Sequential points in time are identified with t.sub.1 to t.sub.10.

(37) At the first point in time t.sub.1, a start signal is generated to drive the product conveyor belt. For a set duration between the first point in time t.sub.1 and the second point in time t.sub.2, the product conveyor belt is operated with an initial torque M.sub.I. The initial torque M.sub.I corresponds to a non-reduced full torque of 100% of the operating torque M.sub.B. The initial torque M.sub.I is applied for an initial time period T.sub.I (here: t.sub.2t.sub.1) until a certain impetus has been achieved.

(38) At the second point in time t.sub.2, the torque is reduced to a ramp starting torque M.sub.RS which is about 30% of the full operating torque M.sub.B. Then the torque is increased substantially linearly and gradually for a rise time period T.sub.S until it reaches the full operating torque at the third point in time t.sub.3. The increase is carried out using phase-start cutting and/or phase-end cutting and lasts over the rise time period T.sub.S which in this case is t.sub.3t.sub.2.

(39) From the third point in time t.sub.3 to the fourth point in time t.sub.4, the full operating torque M.sub.B is applied, and the product conveyor belt is driven normally, for example with a substantially constant TARGET transport speed. At the fourth point in time t.sub.4, a stop signal is generated, and the product conveyor belt is braked between the fourth point in time t.sub.4 and fifth point in time t.sub.5 to 0% of the torque. Braking is essentially linear and gradual using phase-start cutting and/or phase-end cutting. The braking is configured such that it normally occurs over a predetermined time period, i.e., the slope time period T.sub.N (here: t.sub.5t.sub.4). The slope time period T.sub.N corresponds to the time period over which the applied torque M(t) is reduced from the operating torque M.sub.B to zero.

(40) Once the applied torque M(t) is reduced to zero, i.e., at the fifth point in time t.sub.5 in the shown example, a dead point in time T.sub.T is started.

(41) At the sixth point in time t.sub.6, a new start signal is generated. A check by the control unit shows that less time has passed between the fifth point in time t.sub.5 and the sixth point in time t.sub.6 than the second dead time of for example 1 s. Consequently, the product conveyor belt is not immediately started; instead, no torque is initially applied up to the seventh point in time t.sub.7. At the seventh point in time t.sub.7, the dead time has expired (measured from the complete stop of the product conveyor belt to the fifth point in time t.sub.5), and a new acceleration cycle is started. In other words, the following applies for the exemplary embodiment: T.sub.T=t.sub.7t.sub.5.

(42) For a set duration between the seventh point in time t.sub.7 and the eighth point in time t.sub.8, the product conveyor belt is again driven with the initial torque M.sub.I of 100% of the operating torque M.sub.B until a certain impetus has been achieved once again for the set initial time period T.sub.I.

(43) At the eighth point in time t.sub.8, the applied torque is reduced to the ramp starting torque M.sub.RS which is about 30% of the full operating torque M.sub.B. Then the applied torque M(t) is increased substantially linearly and gradually up to a ninth point in time t.sub.9 until a stop signal is generated before 100% of the operating torque M.sub.B is reached.

(44) Then the product conveyor belt is braked between the ninth point in time t.sub.9 and the tenth point in time t.sub.10 to 0% of the torque.

(45) In an exemplary embodiment, at least one of the following parameters of the control box 70 and/or the control unit 80 can be set: the length of the initial time period T.sub.I, i.e., the time period of driving with full initial torque M.sub.I when starting the product conveyor belt; the length of the dead time T.sub.R, i.e., the time period before the renewed beginning of the acceleration after braking the product conveyor belt; and/or the size of the ramp starting torque M.sub.RS, i.e., the starting point for the acceleration ramp.

(46) Preferably, all three of these parameters can be adjusted in order to adapt the control box 70 and/or the control unit 80 to the special conditions of the checkout system.

REFERENCE NUMBER LIST

(47) 10 Alternating current source 20 Rectifier 30 Microcontroller 40 Trigger 50 Phase-start cutting and/or phase-end cutting controller 60 Drive motor 70 Control box 80 Control unit 81 Motor output 82 Input 83 Power connection 85 Power supply line M(t) Applied torque M.sub.B Operating torque M.sub.I Initial torque M.sub.RS Ramp starting torque S Current characteristic T.sub.I Initial time period T.sub.N Slope time period T.sub.S Rise time period T.sub.T Dead time P Characteristic of the percentage of power t.sub.1 . . . t.sub.10 first to tenth point in time t.sub.v Point in time at which the full load current is reached Start phase angle