Patent Application
20240109582
The subject matter herein generally relates to the field of resistive torque-generating devices and motor control. More particularly, the subject matter herein relates to tactile feedback device (TFD) brakes used in conjunction with a motor to provide active/semi-active steer-by-wire control for a human-machine interface.
Existing tactile feedback devices (TFDs) may be used for steering position output and semi-active torque feedback for steer-by-wire applications. TFD brakes that typically include one or more sensors to measure steering position, and a coil to activate magnetically responsive (MR) medium such as magnetorheological fluid (MR fluid) or magnetically responsive powder (MR powder) to produce brake torque. TFDs that include an on-board microcontroller, position sensor(s) and amplifiers, collectively referred to as a tactile feedback control unit (TFCU), can communicate with external vehicle controllers to communicate position and control brake feel. TFD's are good at providing end stop control and variable resistive torque. However, TFDs are incapable of providing active features such as return-to-center, command following, on-center control, active force-feel, or warning mode (e.g., similar to an aircraft stick shaker). Conversely, motors used for active control are good at providing the fine motion controlled active features, but provide inadequate end stop control, braking, and resistive torque. When attempts are made to use a motor to obtain an equivalent torque found in a TFD and have that motor provide end stop control, braking, and/or resistive torque, the motor must be significantly larger in size when compared to a brake and use significantly higher current levels to achieve that torque. By only using a motor with sufficient torque to address resistive brake torque as the steer-by-wire system, the motor is very large and it is nearly impossible for a human to provide control via a steering input device to overcome the peak torque.
The solution is to provide a combination TFD brake and relatively smaller motor as a steer-by-wire system capable of generating both tactile feel and shaft motion that are controlled by the TFCU. In this solution, the TFD and the motor work together to maximize their strengths and optimize the performance for the human operator.
A combined brake and motor providing tactile feedback control to a human-machine interface steering input device as part of a steer-by-wire system is provided with this invention. The brake is a tactile feedback device (TFD) brake, and the motor is an electric motor coupled to the brake. The brake provides end stop control and resistive torque to the steer-by-wire system. The motor provides motion control to the steer-by-wire system, where motion control includes a return-to-center, a command following, an on-center control, an active force-feel, and/or a warning mode (e.g., similar to an aircraft stick shaker or a lane departure). The steer-by-wire system is an active system.
In one aspect, a steer-by-wire system providing a steering response is provided. The system comprises a brake, a motor, a shaft, at least one position sensor, and at least one microcontroller. The motor is coupled to the brake. The shaft is coupled to the brake and the motor. The at least one position sensor is capable of providing an angular position of the shaft. The at least one microcontroller contains programming suitable for providing input to the motor and the brake to create the steering response, wherein the brake, the motor and the position sensor are in electronic communication with the microcontroller.
In another aspect, a method of providing a steering response in a vehicle is provided. The method comprising an operator driving the vehicle, the driving including the operator steering a vehicle steering system, rotating the shaft by the operator to provide at least one steering input to the vehicle steering system, translating the at least one steering input into an electronic steering command with the steer-by-wire system, communicating the steering angular position to a steering controller from the at least one microcontroller, and providing a semi-active tactile feedback to the operator, the semi-active tactile feedback creating the steering response which simulates a direct linkage steering system. The vehicle steering system has a steer-by-wire system that is capable of providing the steering response, the steer-by-wire system including a brake, a motor coupled to the brake, a shaft coupled to the brake or the motor, at least one position sensor capable of generating and providing an angular position signal of the shaft, at least one microcontroller capable of providing input to the motor and the brake to create the steering response, wherein the brake, the motor and the position sensor are in electronic communication with the at least one microcontroller.
Current tactile feedback devices (TFDs) are predominately brakes including magnetorheological fluid (MR fluid) or magnetically responsive powder (MR powder) and are used for steering position output and semi-active torque feedback for steer-by-wire applications. These devices include one or more sensors to measure steering position, and a brake coil to activate MR fluid or MR powder to produce a braking torque. As disclosed herein, the TFD is coupled with a motor to at least overcome the “off-state” torque of the device. This minimum torque is the torque necessary to provide motion control such as return-to-center, command following, on-center control, active force-feel, or warning mode.
In the embodiments disclosed herein, a brake is combined with a motor to provide steer-by-wire control for the human-machine interface. The combination may be referred to as an active hybrid steer-by-wire system.
In many cases the human-machine interface is a steering input device such as a wheel or yoke, but it can also be a control stick or a joystick, as well as any other device that can provide control input from a human and require a tactile feedback.
The brake described below is a TFD brake, but the system can use any brake that is capable of providing end stop control, braking, and/or resistive torque. Thus, the usage of a TFD brake herein is meant only to be a representative type of brake and it is not meant to be limiting to only a TFD brake, or a MR TFD brake.
Referring to
Shaft 16 is directly or indirectly coupled to steering input device 28. Microcontroller 22 is in electronic communication with steering controller 30, vehicle controller 32, and/or CAN bus 34 (Controller Area Network bus). Alternatively, microcontroller 22 is in electronic communication with steering controller 30 and/or vehicle controller 32 via CAN bus 34. Microcontroller 22 is able to receive electronic communications from steering controller 30 and/or vehicle controller 32 directly or via CAN bus 34. Steering controller 30 and/or vehicle controller 32 are collectively referred to as external controllers.
Any motor 14 can be used in this application, but a frameless brushless direct current motor (BLDC) is referred to herein as an acceptable solution. However, the use of a BLDC motor is not meant to limit the invention to only a BLDC motor. The frameless design of the BLDC motor 14 allows for easier mechanical integration in-line with brake 12, while the brushless design ensures long life and low maintenance. When combined with brake 12, motor 14 is positioned to actively control shaft 16.
Motor control is performed using output(s) from position sensor 18 along with appropriate commutation electronics. Motor 14 includes motor rotor 64, and stator 66 and at least one winding coil (not shown). Motor rotor 64 rotates with shaft 16 which either passes through motor rotor 64 or is mated to motor rotor 64. At least one optional amplifier 24 capable of transmitting a variable current through the at least one winding coil may be used. The same or a different optional amplifier 24 may be used to transmit and receive signals with brake 12.
In the embodiments illustrated in
Brake 12 may be a TFD brake, a drum brake, a disk brake, a friction brake, an electromagnetic brake, or combinations thereof. For illustrations purposes only,
In some embodiments, housing 38 has at least a portion of motor 14 positioned within housing 38. As illustrated in
Shaft 16 is rotatably disposed within housing 38 and motor housing 62. In some embodiments, shaft adapter 72 supports shaft 16 with motor rotor 64 and stator 66 positioned outwardly therefrom. As illustrated, shaft 16 is rotatably supported by upper bearings 74 and lower bearings 76, along with shaft adapter 72. In the TFD drum brake 12 configuration, shaft 16 has rotation disk 78 attached thereto and extending radially outward therefrom. Drum rotor 40 is connected to rotation disk 78 at end 80 of rotation disk 78 and rotates with shaft 16. As illustrated in
In this configuration, TFD drum brake 12 provides braking, end stop control, and resistive torque. Brake 12 is able to provide a peak resistive force between 5 Newton meters and 25 Newton meters; however, the commonly desired peak resistive force will vary with the application of the TFD system. Motor 14 provides motion control to include return-to-center, command following, on-center control, active force-feel, or warning mode (e.g., similar to an aircraft stick shaker or a lane departure). In one embodiment, the warning mode involves an active pulsation input to shaft 16 in order to create vibratory feedback and indicate a specific warning or abnormal vehicle condition. Motor 14 can also be used for command following applications. For example, if a vehicle is being steered autonomously using global position system guided navigation, then movements of steering input device 28 will follow the actual vehicle movements. Similarly, when used on a boat having two steering input stations, movement of the steering input station not in use is synchronized with the steering input station in use. In this way, the two steering input devices 28 have matching movements.
Motor 14 is able to provide a force between about 0.5 Newton meters and about 5 Newton meters. Also, motor 14 is able to provide a force that exceeds an off-state brake torque level between about 0.01% and about 25.0% of a maximum possible resistive brake torque for brake 12. Device 10 in this configuration limits the amount of torque generated in steering input device from motor 14, and is safe for steer-by-wire applications since it cannot overwhelm the operator. Steer-by-wire systems 10 provide an artificial steering response to the operator through steering input device 28.
Microcontroller 22 controls both TFD brake 12 and motor 14. Position sensor 18 provides communication of the angular position of shaft 16 to the microcontroller. Additional sensors (not illustrated) may also communicate brake 12, motor 14, and shaft 16 information to microcontroller 22. Microcontroller 22 may be a single microcontroller providing control over both brake 12 and motor 14. Alternatively, microcontroller 22 may be two more microcontrollers 22 with at least one dedicated to controlling brake 12 and one dedicated to controlling motor 14.
Position sensor 18 comprises one or more sensors. Position sensor 18 may be an absolute position sensor, an optical position sensor, a Hall effect sensor, an encoder, a resolver, or combinations thereof. Position sensor 18 is capable of measuring an angular position of shaft 16 and communicating those measurements to microcontroller 22. Position sensor 18 may be in direct electronic communication, indirect electronic communication, or both direct electronic communication and indirect electronic communication with an external controller such as steering controller 30 and/or vehicle controller 32. The external controller is separate from microcontroller 22 in steer-by-wire system 10. As known to those skilled in the art, each described version of sensor 18 will “read” a location point on the end of shaft 16. For example, when using a Hall effect sensor 18, a magnet 19 will be located in the end of shaft 16.
In one embodiment, position sensors 18 are non-contact sensors. The sensor measurements are used by microcontroller 22, along with along with advanced motion control algorithms, to control rotation of shaft 16, and when idle return shaft 16 back to center when the operator is not operating steering input device 28. An example of a suitable motion control algorithm is provided in
In an embodiment with two or more position sensors 18, position sensors 18 are able to provide shaft 16 angular position within a margin of error between about −5 degrees to about +5 degrees. For a more refined device 10, position sensors 18 are able to provide a shaft 16 angular position within a margin of error of about ±3 degrees, or a shaft 16 angular position within a margin of error of at least ±1 degrees. The location of each sensor 18 will be selected to provide the degree of accuracy needed for the system, e.g. one sensor 18 on top of the printed circuit board supporting the microcontroller and one sensor 18 underneath the printed circuit board. In one embodiment, the disclosed steer-by-wire system 10 does not require a gear pack or an assembly of gears between shaft 16 and the position sensor 18 to support or drive position sensor 18. As a result, in the disclosed invention, position sensors 18 may be on axis and in-line with shaft 16. Locating positions sensors 18 on the axis of shaft 16 reduces the complexity of the sensor assembly thereby reducing the number of potential failure modes and mechanical noise. Additionally, the configuration of components provides manufacturing efficiencies. However, off-axis locations of position sensors 18 will also perform satisfactorily in the steer-by-wire system 10.
In operation, motor 14 is capable of providing an input to induce an artificial steering response for the operator through steering input device 28. The inputs include a return-to-center, an alert warning, a midrange feel, active force feel, wheel traction feel, wheel slip feel, and/or two or more steering synchronizations. Two or more steering synchronizations means that there are two or more steering input devices 28 that are synchronized together to have synchronized movement and response.
In the representative embodiments illustrated in
Microcontroller 22, through control of brake 12 and motor 14, provides a variable tactile feel to the human operator through steering input device 28. Microcontroller 22 controls the braking, end stop control, and resistive torque of brake 12. This is accomplished by controlling the current to integrated coil 44 and/or by providing a command input to brake 12 where the command input produces a braking action that replicates an end-of-travel stop, a normal operation, and/or a resistive force corresponding to an action associated with the steering response.
Additionally, microcontroller 22 is able to communicate commands to motor 14 to provide the motion control. For example, in one embodiment microcontroller 22 provides return-to-center operation capabilities. In this embodiment, microcontroller 22 using position sensor 18 detects movement of steering shaft 16 away from the center position and provides a command to motor 14 to return shaft 16 to a center position. Also, microcontroller 22 is able to communicate commands to motor 14 suitable for controlling the angular position of shaft 16, introducing a warning command/mode to shaft 16 causing shaft 16 to vibrate or dither, providing on-center control, and/or providing an active force-feel input to shaft 16.
Microcontroller 22 is able to estimate torque experienced by shaft 16 from the current being used by device 10. Additionally, to provide the previously discussed control operations, microcontroller 22 is able to receive and process measurements of the angular position of shaft 16 from one or more position sensors 18. Preferably, each position sensor 18 is located in alignment with the axis of shaft 16.
In operation, microcontroller 22 is able to command motor 14 with one or more currents having a specific phase difference for commutation and is able to turn motor 14 in a desired direction in order to provide the motion control input to shaft 16.
Referring to
Device 10 is capable of being installed on a vehicle (not shown) where an active steer-by-wire system is desired. Type of vehicles may be construction vehicles, agriculture vehicles, forestry vehicles, transportation vehicles, material handling vehicles, marine craft, and aircraft.
Referring to
The method further includes having an operator drive the vehicle and rotate shaft 16 by providing at least one steering input to the vehicle steering system. The method also includes position sensor 18 translating the steering input into an electronic steering command. The steering angular position determined by position sensor 18 is communicated to a steering controller 30 by microcontroller 22. Device 10 provides a semi-active tactile feedback to the operator. The semi-active tactile feedback creates the artificial steering response which simulates a direct linkage steering system.
In the method, the steering response includes the ability to provide a plurality of electronic steering commands including: an end stop control, a resistive torque, a return-to-center, at least one deviation warning, traction feel, wheel slip feel, on center feel, and/or a steering synchronization.
The semi-active tactile feedback is based on combination of position sensor 18, a calculated steering velocity, i.e. angular velocity, a calculated steering acceleration, i.e. angular acceleration, or a digital input from the steering controller 30. The semi-active tactile feedback includes a constant, periodic or a variable braking torque generated by sending a current through integrated coil 44. As discussed application of the current and control of the current is provided by microcontroller 22.
In the method, the step of rotating shaft 16 further comprises measuring the operator's steering input via shaft 16 by position sensor 18. Position sensor 18 communicates a position signal to microcontroller 22 and/or steering controller 30. Microcontroller 22 or TFCU 24 using microcontroller 22 provides semi-active tactile feedback to the operator through control and adjustment of brake 12 and/or the motor 14.
As described above, the method provides for returning shaft 18 to a center position when position sensor 18 fails to detect the operator providing at least one steering input after a manufacturer selected interval.
The method allows for controlling brake 12 with a first of at least two microcontrollers 22 and controlling motor 14 with a second of at least two microcontrollers 22. Regardless of whether there is one microcontroller 22 or more than one microcontroller 22, the method provides for the microcontroller controlling motor 14 to use an angular position signal from position sensor 18 and be able to calculate the required commutation signals for a brushless direct current (BLDC) motor 14.
Other embodiments of the present invention will be apparent to one skilled in the art. As such, the foregoing description merely enables and describes the general uses and methods of the present invention. Accordingly, the following claims define the true scope of the present invention.
The present application claims priority to U.S. Provisional Application No. 63/146,277, filed on Feb. 5, 2021, which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/015247 | 2/4/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 61146277 | Jan 2009 | US |
