Steer-by-wire system with dynamic braking and end stop cushioning for haptics

Abstract

A haptic feedback mechanism for a steer-by-wire system includes a motor. An electronic circuit includes a node and a switch for controlling the motor. A voltage sensor at the node and a motion sensor for the DC motor feed a motor control logic module operable to: determine if the voltage at the node is above a predetermined threshold; determine if the input motion is above a predetermined speed; and change the switch to an over-current protection mode if the voltage is above the predetermined threshold or the input motion is above the predetermined speed. In the over-current protection mode, electrical power generated by the input motion is dissipated through a resistance and / or the motor while maintaining haptic feedback. An end stop mechanism includes a position sensor coupled to the haptic feedback mechanism for detecting an angular position of the motor to increase a feedback torque near an end stop of the motor.

Description

Technical Field

[0001] This subject matter discloses steer-by-wire systems, and more specifically steer-by-wire systems with dynamic braking and end-stop buffers for enhanced response and performance. Background Technology

[0002] Traditional vehicles steer through a direct mechanical and / or hydraulic linkage between the steering wheel or lever, steering gears, and the actual wheels. With such a system, the driver turns the steering wheel or lever, and the steering gears in turn turn the wheels. The feel of the system is generated by the mechanical linkage, which can be power-assisted. A change in the feel of the system may indicate that one or more components are not functioning correctly or are in an incorrect state, such as wheel imbalance or misalignment.

[0003] To offer various advantages, a steer-by-wire system can replace direct mechanical linkage. In a steer-by-wire system, a position encoder monitors the position of the steering wheel. The position encoder readings are converted into a desired position signal with a steering angle. An electrical signal is sent to the steering control unit to correctly turn the wheels in response to the desired position signal.

[0004] Steer-by-wire systems hold great potential because they eliminate many necessary mechanical connections and components. However, with these systems, rapid movements of the steering wheel by the user can interfere with the desired smooth tactile feedback.

[0005] When using a steer-by-wire system, there is typically a limitation on the range of travel of the control input (i.e., end stops). When the travel limiting mechanism is physical, if the user moves the control input to impact the physical limit, an undesirable experience may occur, such as loud crash noise and / or rebound. Pads are typically used to soften the impact at the end of travel and reduce noise. However, pads may exacerbate rebound from the end of travel and / or reduce the range of travel below desired or acceptable limits. Virtual end stops include magnetic brakes or motors that apply force upon reaching the virtual end stop to simulate the effect of physical limitations. Virtual end stops do not have the crash noise problem, but the tactile feedback is poor, which is undesirable. Summary of the Invention

[0006] In view of the above, there is a need for a steer-by-wire system that provides smooth operation even during rapid movement of the controller (e.g., steering wheel, joystick, and the like) and at the end of the journey.

[0007] Preferably, the steer-by-wire system incorporates dynamic braking in the brushless DC motor, which provides tactile feedback torque to the controller. In another embodiment, the steer-by-wire system creates safe thermal conditions for the brushless DC motor and electronics while dissipating the energy added by user movement of the controller. Preferably, the steer-by-wire system allows for rapid movement of the controller up to or even above 200 rpm.

[0008] In yet another embodiment, the steer-by-wire system has end stops that allow for the full range of travel and prevent collision noise and rebound.

[0009] In one embodiment, this subject matter relates to a haptic feedback mechanism for a steer-by-wire system in a vehicle, the steer-by-wire system having a hand-operable controller for guiding the movement of the vehicle based on input motion from a user. The haptic feedback mechanism includes a DC motor connected to the hand-operable controller for providing haptic feedback to the user based on the input motion. The DC motor has a motor coil. Electronic circuitry includes nodes and at least one pair of switches coupled to the DC motor for controlling the operation of the DC motor. A voltage sensor is coupled to the nodes for generating a voltage signal indicating the voltage at the nodes. A current sensor is coupled to the DC motor for generating a voltage signal indicating the current present in the DC motor (i.e., a DC motor current measurement). A motion sensor is coupled to the DC motor for generating a speed signal indicating the input motion. A motor control logic module is coupled to: at least one pair of switches for controlling the operation of the DC motor; a voltage sensor for receiving the voltage signal; a current sensor for receiving the DC motor current measurement; and a motion sensor for receiving the speed signal. The motor control logic module operates to: determine whether the current in the DC motor current measurement exceeds the current requested by the motor control logic module; determine whether the voltage at the node is higher than a predetermined threshold; determine whether the input movement of the hand-operated controller exceeds a predetermined speed; and if the voltage exceeds the predetermined threshold or the input movement exceeds the predetermined speed, then at least one pair of switches is switched to an overcurrent prevention mode. In the overcurrent prevention mode, a braking algorithm is applied to the DC motor for a predetermined period of time during which the electrical power generated by the input movement is dissipated through the resistance of at least one of the switches and the motor coil, while maintaining tactile feedback to the user. An optional end stop mechanism includes a position sensor coupled to the tactile feedback mechanism for detecting the angular position of the motor or the hand-operated controller, wherein the tactile feedback mechanism increases feedback torque within a predetermined range of the end point of travel of the DC motor or the hand-operated controller.

[0010] The switch assembly may also include at least one braking resistor connected in series with the switch, which is connected in parallel with the pair of switches to provide further resistance for dissipating electrical power. The predetermined time period may be based on the maximum possible duration of the high-speed input conditions. Preferably, the electrical power is dissipated as heat and / or the predetermined time period is based on the time required to dissipate the heat. At least two switches may be three pairs of switches connected in parallel, each pair having a high-side switch and a low-side switch, such that in overcurrent protection mode, the high-side switch is always open and the low-side switch is periodically closed to balance power dissipation and desired tactile sensation. The sensor assembly may also include a DC power supply circuit, wherein the three pairs of switches are configured in a half-bridge between the DC motor and the DC power supply circuit.

[0011] Another embodiment of this subject matter relates to an end stop mechanism for a steer-by-wire system for steering a vehicle, the steer-by-wire system having a hand-operated controller for guiding the movement of the vehicle. The end stop mechanism includes a haptic feedback mechanism having a motor coupled to the hand-operated controller for providing feedback torque to the hand-operated controller. A position sensor is coupled to the haptic feedback mechanism for detecting the angular position of the motor or the hand-operated controller, wherein the haptic feedback mechanism increases the feedback torque within a predetermined range at the end point of travel of the motor or the hand-operated controller.

[0012] The end stop mechanism may further include a speed sensor coupled to a haptic feedback mechanism for detecting the speed of the hand-operated controller, wherein the feedback torque is adjusted by modifying the damping coefficient to be proportional to the speed and proximity to the end point within a predetermined range. Preferably, when the direction of travel changes away from the end point, the haptic feedback mechanism resets the speed damping coefficient to one to restore normal operation within a predetermined range. The hand-operated controller may be a steering wheel, joystick, joystick combination, and the like.

[0013] It should be understood that the techniques described herein can be implemented and utilized in various ways, including but not limited to processes, apparatuses, systems, devices, methods for applications now known and hereafter developed, or as computer-readable media. These and other unique features of the systems disclosed herein will become more apparent from the following description and accompanying drawings. Attached Figure Description

[0014] To facilitate a better understanding by those skilled in the art of manufacturing and using the present disclosure, reference may be made to the following figures.

[0015] Figure 1 This is a schematic diagram of a steer-by-wire system disclosed in this subject matter.

[0016] Figure 2This is a schematic diagram of a DC motor and associated electronic equipment for a steer-by-wire system disclosed in this subject matter.

[0017] Figure 3 This is a schematic diagram of a DC motor and associated electronic equipment for a steering-by-wire system in overcurrent prevention mode, as disclosed in this subject matter.

[0018] Figure 3A This is a schematic diagram of another DC motor and associated electronics for a steering-by-wire system in overcurrent prevention mode, as disclosed in this subject matter.

[0019] Figure 4 It is a diagram of the speed damping coefficient versus position of a steer-by-wire system with end stop buffers disclosed in this subject matter. Detailed Implementation

[0020] This subject matter overcomes many problems of the prior art associated with steer-by-wire systems and methods. The advantages and other features of the technology disclosed herein will become more apparent to those skilled in the art through the following detailed description of certain preferred embodiments, taken in conjunction with the accompanying drawings illustrating representative embodiments of the technology (and wherein similar reference numerals identify similar structural elements). Directional indications such as up, down, right, left, and similar directions are used relative to the drawings and are not intended to be limiting.

[0021] Now for reference Figure 1 A schematic diagram of a steer-by-wire system 100 disclosed in this subject matter is shown. The steer-by-wire system 100 has no mechanical or hydraulic connection between the user and the mechanism for directional wheels. The system 100 has a controller 102 for a user connected to a steering column 104, such as a joystick or steering wheel. The column 104 is coupled to a haptic feedback mechanism 106. The haptic feedback mechanism 106 communicates with a steering control unit (SCU) 108. The haptic feedback mechanism 106 and the SCU 108 are shown as distinct but may be partially or wholly integrated into a single unit, such as an SCU 108 including a submodule of the haptic feedback mechanism. The SCU 108 can convert column movement into actuator control signals. The actuator control signals are sent to actuator 110, which drives the desired movement of the steering mechanism 112, causing the wheels 114 to rotate in a desired manner.

[0022] Now for reference Figure 2A schematic diagram of a haptic feedback mechanism 106 for a steer-by-wire system 100 is shown. The haptic feedback mechanism 106 includes a DC motor 120 coupled to a steering column 104 to provide haptic feedback torque to create a conventional operating experience for the user. Preferably, the DC motor 120 is a three-phase brushless DC motor. A sensor assembly 122 is coupled to the motor 120 to generate a signal indicating a shaft angular position measurement and send it to a motor control logic module 124. In other words, the sensor assembly 122 determines the rotational speed of the steering column 104. The sensor assembly 122 may be one or more separate sensors that measure various parameters according to the art of the subject. Sensors may be coupled to the motor, steering column, steering wheel, and similar locations as needed to generate signals indicating information used in the art of the subject. Similarly, in joysticks or other applications, sensors may be placed in various locations as needed. One embodiment of the sensor assembly 122 includes a sensor configured to measure the current of the DC motor 120.

[0023] The motor control logic module 124 is also electrically connected to the electronics 126 for driving the DC motor 120. Preferably, the motor control logic module 124 uses a pulse width modulation (PWM) control signal with a predefined duty cycle for motor control. As shown, the drive electronics 126 and the software can be partially or wholly integrated into the SCU 108 or into the haptic feedback mechanism 106. In either case, the haptic feedback mechanism 106 and / or the SCU 108 control the commutation of the DC motor 120 and all other aspects of control.

[0024] Preferably, the drive electronics 126 includes a three-phase half-bridge driver configuration comprising three switch assemblies 128 controlled by the motor control logic module 124 of the haptic feedback mechanism 106. Each switch assembly 128 includes a pair of switches 130a, 130b connected in series with an optional current-sensing resistor 132. The current-sensing resistor 132 allows measurement of the current in each phase of the DC motor 120 for precise haptic control of the DC motor 120. Therefore, the total current in the DC motor 120 is known. In one embodiment, the current-sensing resistor 132 converts the phase current into a voltage signal, which is used by the motor control logic 124 to calculate the total current in the motor 120.

[0025] Switch 130a is a high-side switch. Switch 130b is a low-side switch. Each switch 130a, 130b is connected in parallel with diode 134. Each switch 130a, 130b is preferably a MOSFET switch. Switch assembly 128 is connected in parallel with power supply circuit 136. Power supply circuit 136 includes DC motor power supply 138, capacitor 140, and diode 142.

[0026] In addition to the shaft angular position measurement signal, the motor control logic module 124 also receives current feedback data from the drive electronics 126. Sensor 144 at supply node 146 in the drive electronics 126 is a voltage sensor that communicates with the motor control logic 124. Based on the signal from sensor 144, the motor control logic can determine whether an overvoltage condition exists at the DC motor power supply 138. As can be seen, the signal from sensor 144 indicating the voltage at supply node 146 can be effectively used to determine the current in the DC motor 120. Furthermore, the motor control logic module 124 also receives data regarding torque commands from the SCU 108.

[0027] In operation, switches 130a and 130b are turned on and off according to an algorithm to supply current to the phase of motor 120, thereby generating tactile torque for the steering wheel or joystick 102 for the user. In other words, the current in motor 120 is set by controlling the amount of voltage supplied to motor 120, and the feedback torque on motor 120 varies based on sensed inputs and data received by motor control logic module 124. However, when the user moves the steering wheel or joystick 102 quickly, a large amount of mechanical power can be input to the tactile feedback mechanism 106. The input mechanical power is applied to motor 120, causing motor 120 to act as a generator to convert the input mechanical power into current. The generated current is undesirable because it may trigger protective measures that reduce the motor torque feedback to zero. A reduction in motor torque feedback to zero is undesirable because the steering wheel or joystick 102 will lose its desired feel. For example, the user might perceive a loss of control without tactile feedback, even if control may still be present, potentially leading to unsafe driving conditions.

[0028] To prevent a reduction in motor torque feedback, the motor control logic module 124 uses a current-sensing resistor 132 to monitor the current in the motor 120, a sensor assembly 122 to monitor the motor shaft rotation speed, and a voltage sensor 144 to monitor the voltage at the supply node 146. Any or all of the resistor 132, sensor assembly 122, and voltage sensor 144 can be used to avoid a reduction in motor torque feedback by switching to an overcurrent protection mode. For example, the motor control logic module 124 can determine when an overcurrent condition is about to occur based on a current measurement from the current-sensing resistor 132 exceeding the current requested by the motor control logic module 124, combined with rotational speed readings from the sensor assembly 122 and / or voltage signals from the sensor 144. When an overvoltage condition is about to occur or has already occurred, the SCU 108 prevents a reduction in motor torque feedback through management operations to maintain the user's desired smooth experience (e.g., entering an overcurrent protection mode).

[0029] Now for reference Figure 3 A schematic diagram of the haptic feedback mechanism 106 for the steering-by-wire system 100 in overcurrent protection mode is shown. When a motor torque feedback reduction event occurs, the motor control logic module 124 applies a braking operation algorithm, which disconnects all three high-side switches 130a while simultaneously closing all three low-side switches 130b to form a circuit. Therefore, unwanted current flows through the resistance of the switches 130b and the coils (not explicitly shown) of the motor 120 [KMI] to dissipate the input power as heat. Based on the maximum possible duration of the high-speed input conditions and / or the time required to dissipate the generated heat, the braking operation algorithm is applied for a predetermined time period, allowing the feedback motor 120 to maintain normal operation and quickly exit the overcurrent protection mode. For example, the maximum possible duration could be the amount of time at the current speed before reaching an actual physical hard stop. In an alternative embodiment, when a motor torque feedback reduction event occurs or is about to occur, the motor control logic module 124 disconnects all three low-side switches 130b while simultaneously closing all three high-side switches 130a to achieve the same effect. In other words, the motor control logic module 124 completes the circuitry to allow current to flow through the motor coils (and elsewhere) for dissipation, while simultaneously using unwanted overcurrent in the motor 120 to generate tactile force on the steering wheel 102.

[0030] In another embodiment, the total current entering all three switch assemblies 128 is measured using a single sensing resistor (not shown) instead of three sensing resistors 132. Therefore, the number of current sensors is reduced to one.

[0031] Now for reference Figure 3A Another embodiment of a haptic feedback mechanism 206 for a steer-by-wire system is schematically illustrated. Components similar to those described in connection with the above embodiments are indicated by similar reference numerals of the 200 series. Many components are substantially the same as those in the foregoing embodiments and therefore will not be described further herein. The main difference is the addition of one or more braking resistors to selectively provide further dissipation of input power in overcurrent protection mode. The haptic feedback mechanism 206 includes a resistor 250 connected in parallel with a capacitor 240 and a switch assembly 228. A switch 252 is connected in series with the resistor 250. Motor control logic 224 determines when the switch 252 is open to remove the resistor 250 from the haptic feedback mechanism 206, or when the switch 252 is closed to insert the resistor 250 into the haptic feedback mechanism 206.

[0032] When a motor torque feedback reduction event occurs, the motor control logic module 224 enters overcurrent protection mode and applies a braking operation algorithm, which disconnects all three high-side switches 230a while simultaneously closing all three low-side switches 230b. Furthermore, the motor control logic 224 closes switch 252, causing the additional input power to be dissipated as heat (as described above) through resistor 250. Therefore, the ability to dissipate potentially dangerous overcurrents is increased. Consequently, the braking operation algorithm can be applied for a shorter duration. During normal operation, switch 252 is open, meaning resistor 250 is not actually in the circuit.

[0033] It is conceivable that the SCU 108 and the haptic feedback mechanism 106 can be integrated or separated (wherein the functions are distributed in any way). Thus, each of the SCU 108 and the mechanism 106 can have a signal processing device. For example, both the SCU 108 and the motor control logic module 124 can have a microprocessor, memory, and necessary associated components, such as wireless communication components. Alternatively or additionally, either can be a fully or partially application-specific integrated circuit (ASIC). In short, any type of general-purpose or special-purpose, processor-controlled device capable of receiving, processing, storing, and / or transmitting data can be efficiently adapted to the subject matter. The processor is typically a logic circuit that responds to and processes instructions driving a digital data processing device, and can include, but is not limited to, a central processing unit, an arithmetic logic unit, an ASIC, a task engine, and / or any combination, arrangement, or multiplication thereof. Software or code is present. Software generally refers to computer instructions that, when executed on one or more digital data processing devices, cause interaction with operating parameters, sequence data / parameters, database entries, network connection parameters / data, variables, constants, software libraries, and / or any other elements necessary for the correct execution of instructions within the execution environment of the digital data processing device's memory. However, many such functions performed by software can also be encoded into circuitry or otherwise hardwired. Those skilled in the art will recognize that the functions and various processes discussed herein are merely examples of functions performed by the disclosed techniques, and therefore such processes and / or their equivalents can be implemented in various combinations and numbers in commercial embodiments without materially affecting the operation of the disclosed techniques.

[0034] This subject matter also includes end stops for steer-by-wire systems. (See again...) Figure 1-3Depending on how the electronics are configured, the end stop mechanism includes a haptic feedback mechanism 106 and / or an SCU 108. In addition to the shaft angle measurement sensor, the sensor assembly 122 also includes a speed sensor (not explicitly shown) to measure shaft speed in addition to position measurement. The speed sensor is preferably separate and coupled to the steering wheel or joystick 102 or column 104 to measure the rotational speed of the steering wheel or joystick 102. As the steering wheel or joystick 102 approaches a predetermined endpoint, the haptic feedback mechanism increases the feedback torque to soften and / or prevent collision at the endpoint. Furthermore, the haptic feedback mechanism can increase the feedback torque based on the speed at which the user moves the steering wheel or joystick 102 toward the endpoint. Therefore, the user experiences a cushioned feel as they approach the endpoint, resulting in an overall smooth haptic experience without the need for physical cushioning.

[0035] Now for reference Figure 4 A graph 400 showing the speed damping coefficient versus position of a steering-by-wire system with end stop buffers disclosed in this subject matter is shown. The vertical axis is the speed damping coefficient, and the horizontal axis is the angular position in radians. The haptic feedback mechanism 106 uses sensor assembly 122 to monitor the angular position of the motor shaft and the rotational speed of the shaft.

[0036] During normal operation, the speed damping coefficient is one. Therefore, multiplying the feedback torque by the speed damping coefficient has no effect. Figure 4 In the diagram, the initial portion 402 indicates normal operation within a range of approximately 0-80 radians. As described above, the haptic feedback mechanism 106 provides feedback torque in the direction of travel of the steering wheel, thus providing the user with a smooth tactile experience.

[0037] When the motor shaft angular position approaches a predetermined range R of the physical travel endpoint, the haptic feedback mechanism 106 begins to increase the speed damping coefficient in a manner proportional to the rotational speed and inversely proportional to the remaining travel. Therefore, as the user approaches the end stop, the haptic force applied to the steering wheel or joystick will increase.

[0038] exist Figure 4 In the example shown, the predetermined range R is approximately the last 20% of the travel, and the end stop is at approximately 100 radians. Within the predetermined range R shown as segment 404 in Figure 1, the velocity damping coefficient increases from 1 to approximately 2. In one embodiment, this results in a doubling of the feedback torque, with a more significant increase near the end stop rather than a gradual linear increase. This increase in feedback torque, opposite to the direction of motion, helps to slow the motion and prevent hard impacts, thus creating an effective end stop buffer that does not physically limit the range of travel or add additional complex components.

[0039] When the direction of travel changes away from the end stop, the tactile feedback mechanism 106 resets the speed damping coefficient to one, as shown in section 406 of the figure. Therefore, the tactile feedback of the steer-by-wire system 100 returns to normal.

[0040] Those skilled in the art will understand that, in alternative embodiments, the functionality of several elements can be performed by fewer elements or a single element. Similarly, in some embodiments, any functional element may perform fewer or different operations compared to the operations described with respect to the illustrated embodiments. Furthermore, functional elements described and / or shown as different for illustrative purposes (e.g., modules, connections, sensors, interfaces, hardware, resistors, switches, and the like) may be incorporated into other functional elements in a particular embodiment. It should also be noted that all of the following claims may be combined and referenced in any combination, including multiple references.

[0041] Although the subject matter has been described with respect to preferred embodiments, those skilled in the art will readily understand that various changes and / or modifications can be made to the subject matter without departing from the spirit or scope of the invention as defined by the appended claims.

Claims

1. A haptic feedback mechanism for a steer-by-wire system in a vehicle, the steer-by-wire system having a hand operable controller for directing motion of the vehicle based on input motion from a user, the haptic feedback mechanism comprising: a DC motor connected to the hand operable controller and configured to provide haptic feedback to the user; an electronic circuit configured to control operation of the DC motor, wherein the electronic circuit includes a node; a voltage sensor coupled to the node and configured to generate a first signal indicative of a voltage at the node, the voltage at the node indicative of a current of the DC motor; at least one current sense resistor coupled to the DC motor and configured to generate a second signal indicative of a current in the DC motor; a sensor assembly operatively coupled to the DC motor and configured to generate a speed signal indicative of a rotational speed of the input motion; a motor control logic module operatively connected to: the electronic circuit; the voltage sensor and configured to receive the first signal; the at least one current sense resistor and configured to receive the second signal; and the sensor assembly and configured to receive the speed signal, the motor control logic module operative to: make a first determination, based on the first signal, as to whether the voltage at the node is above a predetermined threshold; make a second determination, based on the second signal, as to whether the current of the DC motor is above a current requested by the motor control logic; make a third determination, based on the speed signal, as to whether the rotational speed is too high; and change the DC motor to an overcurrent prevention mode based on at least one of the first determination, the second determination, and the third determination, wherein, in the overcurrent prevention mode, the motor control logic module uses the electronic circuit to control the DC motor for a predetermined period of time in which electrical power generated by the input motion is dissipated through the DC motor while maintaining the haptic feedback of the user; and an end stop mechanism including a position sensor configured to detect an angular position of the hand operable controller, wherein the motor control logic module uses the electronic circuit to increase a feedback torque within a predetermined range of an end of travel of the DC motor or the hand operable controller.

2. A haptic feedback mechanism for a steer-by-wire system in a vehicle, the steer-by-wire system having a hand operable controller for directing motion of the vehicle based on input motion from a user, the haptic feedback mechanism comprising: a DC motor connected to the hand operable controller and configured to provide haptic feedback to the user, the DC motor having a motor coil; an electronic circuit coupled to the DC motor and configured to control operation of the DC motor; at least one sensor coupled to the DC motor or the electronic circuit and configured to generate a protection signal indicative of a motor current in the DC motor; and ​ a motor control logic module coupled to: the electronic circuit, and the motor control logic module configured to control the electronic circuit; and the at least one sensor, the motor control logic module operative to change the electronic circuit to an overcurrent prevention mode based on the protection signal, wherein, in the overcurrent prevention mode, the electronic circuit causes overcurrent to pass through the motor coil to dissipate the overcurrent while maintaining the haptic feedback to the user.

3. The haptic feedback mechanism for a steer-by-wire system according to claim 2, wherein, the at least one sensor selected from the group consisting of: a voltage sensor coupled to the electronic circuit and configured to generate a first signal indicative of current in the DC motor; at least one current sense resistor in the electronic circuit and configured to generate a second signal indicative of current in the DC motor; a motion sensor coupled to the DC motor and configured to generate a speed signal indicative of the input motion; and combinations thereof.

4. The haptic feedback mechanism for a steer-by-wire system of claim 3, the motor control logic module operative to: make a first determination, based on the first signal and / or the second signal, as to whether the current in the DC motor is above a predetermined threshold; make a second determination, based on the speed signal, as to whether the input motion of the available hand-operable controller is above a predetermined speed; and change the electronic circuit to the overcurrent prevention mode based on the first determination and the second determination.

5. The haptic feedback mechanism for a steer-by-wire system of claim 2, further comprising at least one braking resistor and at least one braking resistor switch in the electronic circuit and configured to selectively connect the at least one braking resistor to provide supplemental resistance to further dissipate power in the overcurrent prevention mode.

6. The haptic feedback mechanism for a steer-by-wire system of claim 2, wherein, the overcurrent prevention mode persists for a predetermined period of time based on a maximum possible duration of a high-speed input condition.

7. The haptic feedback mechanism for a steer-by-wire system of claim 2, wherein, electrical power associated with the overcurrent is dissipated as heat, and the overcurrent prevention mode persists for a predetermined period of time based on a time required to dissipate the heat.

8. The haptic feedback mechanism for a steer-by-wire system of claim 2, wherein, the electronic circuit includes three pairs of switches in parallel, each pair having a high-side switch and a low-side switch, such that, in the overcurrent prevention mode, the high-side switches are open and the low-side switches are periodically closed to maintain the haptic feedback to the user.

9. The haptic feedback mechanism for a steer-by-wire system of claim 8, further comprising a DC power supply circuit, wherein, the three pairs of switches are configured in a half-bridge between the DC motor and the DC power circuit.

10. An end stop mechanism for a steer-by-wire system in a vehicle, the steer-by-wire system having an available hand-operable controller for directing motion of the vehicle, the end stop mechanism comprising: the haptic feedback mechanism of claim 2, wherein the DC motor provides a feedback torque on the available hand-operable controller; and a position sensor coupled to the haptic feedback mechanism for detecting an angular position of the DC motor or the available hand-operable controller, wherein the haptic feedback mechanism increases the feedback torque within a predetermined range of an end of travel of the DC motor or the hand operable controller.

11. The end stop mechanism for a steer-by-wire system of claim 10, further comprising a speed sensor coupled to the haptic feedback mechanism for detecting a speed of the manually operable controller, wherein, The feedback torque is adjusted by modifying a speed damping coefficient proportional to the speed and proximity to the end of travel within the predetermined range.

12. An end stop mechanism for a steer-by-wire system according to claim 11, wherein, The haptic feedback mechanism resets the speed damping coefficient to one for normal operation within the predetermined range when the direction of travel changes away from the end of travel.

13. The end stop mechanism for a steer-by-wire system of claim 10, wherein, The feedback torque is adjusted by modifying a damping coefficient proportional to the speed of the hand operable controller and inversely proportional to the proximity to the end of travel.

14. An end stop mechanism for a steer-by-wire system according to claim 13, wherein, The damping coefficient has a nominal value of one outside the predetermined range and when the direction of travel is away from the end of travel.

15. The end stop mechanism for a steer-by-wire system of claim 10, wherein, The hand operable controller is a steering wheel.

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