Patent Application
20070159126
The present invention relates to a master-slave control system using a bilateral servo control device, and more particularly to a force feedback or parallel bilateral servo control device in which a reaction force of the slave (effecting end) acts on the master (operating end) such that an effecting force awareness can be obtained.
In recent years, classical mechanical controlling/operating devices that have been realized with mechanical mechanisms such as linkage are being replaced with electric controlling/operating devices in which the amount of operation performed by an operator is converted into an electrical signal and an operated article (effecting end) is operated (controlled) with the electrical signal.
Fly-by-wire in aircraft control and X-by-wire in automotive control are good examples, in which a master-slave control system is constructed of a master as an operating end and a slave as an effecting end.
Such systems are constructed as bilateral servo control devices in which a reaction force produced by the movement of the slave is fed back to the master such that an effecting force awareness can be obtained on the master end (see JP Patent Publication (Kokai) Nos. 10-202558 A (1998) and 2003-11838 A, for example).
Bilateral servos can be generally divided into the symmetric type, force-feedback type, force-reflecting type, and parallel type, as noted in a reference document (http://paradise.kz.tsukuba.ac.jp/˜labnhp/labo/study/force/bilateral.html).
Currently, the force-feedback bilateral servo is most widely employed. As model-based control technology develops further and the technology for designing a position command generating unit is established in the future, the parallel bilateral servo, which is the best in terms of characteristics, is expected to become the mainstream.
Of the aforementioned types, the force-feedback type and the parallel type are superior to the symmetric type and the force-reflecting type in terms of operability. However, they require a position (angle) sensor and a force (torque) sensor.
In the force-feedback bilateral servo, the target position (angle) of the slave is determined in accordance with the output of a master position (angle) sensor, and the master is fitted with a force (torque) sensor for improving the response characteristics of the reaction force to the master. Specifically, the slave performs slave position control based on the positional deviation between the master and the slave, while the master performs master force control based on the deviation of force between the master and the slave.
In aircraft and automotive control applications, a mechanical backup mechanism has been provided for failure. However, the demise of mechanical mechanisms makes it necessary to increase the reliability of electrical mechanisms.
Among the X-by-wires by which vehicles are electrically controlled, the steer-by-wire that electrically controls the steering is required to have a particularly high level of reliability because of the absence of the steering position at which safety can be ensured in case of failure (fail-safe position).
Conventional techniques for increasing the reliability of the steer-by-wire include a method whereby a fail-safe is activated upon failure by switching the hydraulic routes for the entirety of the hydraulic pressure (see, e.g., JP Patent Publication (Kokai) No. 7-125643 A (1995)) and a method whereby the vehicle is controlled so that it turns by braking in case of failure of the steer-by-wire system (see, e.g., JP Patent Publication (Kokai) Nos. 11-334559 A (1999) and 2003-63373 A).
While the reliability of the steer-by-wire system can be increased by the aforementioned conventional techniques, more consideration must be given to sensor failures. The conventional techniques had no measure against sensor failures other than to provide multiple sensors. Thus, in order to ensure a predetermined level of reliability, the sensors had to be provided with sufficient redundancy, resulting in an increase in cost.
It is an object of the invention to solve the aforementioned problems and to provide a bilateral servo control device capable of achieving a predetermined level of reliability with lower sensor redundancy.
In order to achieve the aforementioned object, a master position (or angle, in the case of rotary motion) sensor and a force (or torque, in the case of rotary motion) sensor, which are required in a force-feedback and parallel bilateral servo configuration, are used as mutually redundant sensors, so as to increase the reliability of the bilateral servo in which the reaction force from the slave (effecting end) acts on the master (operating end).
The force-feedback bilateral servo device and the parallel bilateral servo device require a position (angle) sensor and a force (torque) sensor. By using these sensors as mutually redundant sensors, resistance against sensor failures can be provided.
Namely, in the force-feedback bilateral servo, a target position (angle) of the slave is determined by the output of the master position (angle) sensor, wherein the master is provided with a force (torque) sensor for improving the response characteristics of reaction force to the master. In accordance with the invention, in the event of failure in the master position (angle) sensor, the slave target position (angle) is determined by the output of the master force (torque) sensor.
In the parallel bilateral servo, a target position (angle) of the slave is determined by the output of the master force (torque) sensor, wherein the master is provided with a position (angle) sensor for improving the response characteristics of reaction force to the master. In accordance with the invention, in the event of failure in the master force (torque) sensor, the slave target position (angle) is determined by the output of the master position (angle) sensor.
In this way, in the force-feedback or parallel bilateral servo control device, the target position (angle) of the slave can be determined by a sensor other than the failed sensor, thus allowing the control operation to proceed.
The invention provides the following bilateral servo control devices (a) to (1):
an operator for determining the control target value of the slave based on the outputs of the first sensor and second sensor of the master.
a proportional calculating unit to which the output of the second sensor is fed and which outputs a value related to the output of the second sensor.
an examination means for determining whether the output of the first sensor is normal or abnormal,
wherein, if the examination means determines that the output of the first sensor is normal, the control target value of the slave is determined based on the output of the first sensor, and if the examination means determines that the output of the first sensor is abnormal, the control target value of the slave is determined based on the output of the second sensor.
an examination means for determining whether the output of the first sensor is normal or abnormal,
wherein, if the examination means determines that the output of the first sensor is normal, the control target value of the slave is determined based on the output of the first sensor, and if the examination means determines that the output of the first sensor is abnormal, the control target value of the slave is determined based on a difference between the output of the second sensor and the control target value of the master.
Thus, in a force-feedback or parallel bilateral servo, the target position (angle) of the slave can be determined by substituting one sensor for another that has failed, thereby allowing a control operation to continue. Furthermore, because the sensors that are originally provided for bilateral servo are utilized as redundant sensors, a control device having a predetermined reliability can be provided with a lower sensor redundancy.
Preferred embodiments of the invention will be hereafter described with reference to the attached drawings.
The bilateral servo control device includes a master 100 as an operating end, a slave 200 as an effecting end, a slave controller 30, and a master controller 40.
The master 100 includes a position (angle) sensor 101 and a force (torque) sensor 102 and produces a normal sensor output (first sensor output) that is a sensor output for the original slave control, and an auxiliary sensor output (second sensor output) that is a sensor output for the reaction force control output of the bilateral servo.
The slave controller 30 receives the normal sensor output and the auxiliary sensor output from the master 100, determines a control target value for the slave 200 based on the normal sensor output and the auxiliary sensor output, and produces a control output Ys based on the thus determined control target value and a sensor output from the slave 200.
The master controller 40 outputs a reaction force control output Ym based on the difference between the auxiliary sensor output and a reaction force target value outputted from the master 100.
In the force-feedback bilateral servo, an output Xm of the position (angle) sensor of the master 100 corresponds to the normal sensor output, and an output Fm of the master force (torque) sensor corresponds to the auxiliary sensor output. On the other hand, in the parallel bilateral servo, the output Fm of the force (torque) sensor of the master 100 corresponds to the normal sensor output and the output Xm of the master position (angle) sensor corresponds to the auxiliary sensor output.
In conventional force-feedback bilateral servos, the output Fm of the force (torque) sensor of the master 100 is not related to the calculation of the control output Ys to the slave 200, so that ∂Ys/∂Fm=0. Similarly, in the conventional parallel bilateral servo, the output Xm of the position (angle) sensor of the master 100 is not related to the calculation of the control output Ys to the slave 200, so that ∂Ys/∂Xm=0.
In the bilateral servo control device of the invention, the amount of operation of the slave 200, namely, the control output Ys, is determined by both the output Xm of the position (angle) sensor and the output Fm of the force (torque) sensor of the master 100, so that ∂Ys/∂Xm≠0 and ∂Ys/∂Fm≠0. In this way, failure of the position sensor and the force sensor of the master 100 can be tolerated.
The position (angle) sensor 101 provided in the master 100 outputs a position (angle) sensor output Xm as a normal sensor output. The position (angle) sensor output Xm constitutes a position (angle) target value for the slave 200. A deviation of the output Xs of the position (angle) sensor 201 of the slave 200 from the target value is calculated at a summing point (calculator) 501 and fed to a servo controller 300.
While not shown, the position (angle) sensor output Xm of the master 100 may be multiplied by a coefficient to calculate the position (angle) target value of the slave 200.
The servo controller 300 produces a control output Ys to the slave 200 based on the deviation between the position (angle) target value Xm and the position (angle) sensor output Xs. A transfer function G(s) of the servo controller 300 in the case of PI control (proportional plus integral control) is determined by:
G(s)=K{1+(1/(Ts))}
where K is gain, T is time constant, and s is a Laplace operator.
Similarly, the output Fs of the force (torque) sensor 202 of the slave 200 constitutes a target value of reaction force to the master 100, and the deviation of the output Fm of the force (torque) sensor 102 of the master 100, which is the auxiliary sensor output, from the reaction force target value that is calculated at the summing point (calculator) 503 is fed to a servo controller 400. The servo controller 400 produces a control output Ym to the master 100 based on the deviation between the reaction force target value Fs and the force (torque) sensor output Fm.
While not shown, the force (torque) sensor output Fs of the slave 200 may be multiplied with a coefficient to calculate the target value of reaction force to the master 100.
The transfer function of the servo controller 400 is determined in the same way as the aforementioned transfer function of the controller 300.
The operations up to this point are the same as those of the conventional force-feedback bilateral servo control device.
Furthermore, in the force-feedback bilateral servo control device of the invention, the force (torque) sensor output Fm of the master 100, which is the auxiliary sensor output, is fed to a summing point (calculator) 502 via a proportional calculation factor (function generator or gain setting unit) 310 having a transfer function H(s). At the summing point 502, the force (torque) sensor output Fm of the master 100 is added to the position (angle) sensor output Xm of the master 100, which is the normal sensor output.
The proportional calculation factor 310 performs a calculation in accordance with a function represented by the transfer function H(s) of the force (torque) sensor output Fm of the master 100 and outputs a value having a correlation with the force (torque) sensor output Fm.
The summed value at the summing point 502 constitutes the position (angle) target value of the slave 200. The deviation of the position (angle) sensor output Xm of the slave 200 from the target value is fed to the servo controller 300, which then produces the control output Ys to the slave 300 based on the deviation.
In accordance with the above-described features of the invention, the slave 200 can be controlled not only by the position (angle) sensor output Xm of the master 100, which is a normal sensor output, but also by the force (torque) sensor output Fm of the master, which is an auxiliary sensor output.
Thus, in case the position (angle) sensor 101 of the master 100, which outputs the normal sensor output, fails, the slave 200 can be controlled by the sensor output Fm of the force (torque) sensor 102 of the master 100, which is the auxiliary sensor output.
In the X-by-wire, to which the invention is particularly directed, the behavior of the slave 200, namely, the vehicle, is fed back via an operator H to the master 100, namely, a controlling/operating unit such as the steering column (steering wheel) or the brake pedal. Therefore, as long as the slave 200 can be controlled by the master 100, no total loss of control would be produced even though a slight deterioration of operability might be caused.
An example of method for generating reaction force in the reaction force generating unit 401 is a method whereby, as shown in
In the case of steer-by-brake, a deceleration sensor 205 (see
In these embodiments, an advantage that relates to the generation of the reaction force target value can be gained that the force (torque) sensor 202 of the slave 200 can be eliminated.
An example of conventional technique for generating reaction force based on the lateral acceleration Gy outputted by a lateral accelerometer is disclosed in JP Patent Publication (Kokai) No. 2003-11838 A. This technique can be applied to the force-feedback bilateral servo control device of the invention, as shown in
A conventional technique for generating reaction force based on the output Xm of a position (angle) sensor of the master 100 is also disclosed in JP Patent Publication (Kokai) No. 2003-11838 A. This technique can be applied to the force-feedback bilateral servo control device of the invention, as shown in
In accordance with the invention, as shown in
In accordance with the conventional technique according to JP Patent Publication (Kokai) No. 2003-11838 A, the vehicle cannot be controlled if the position (angle) sensor 101 for detecting the angle θh of the steering wheel 110 fails. In accordance with the force-feedback bilateral servo control device of the invention, however, steering control of the vehicle can be performed by the servo controller 300 based on the torque Th of the steering wheel 110, namely, the force applied for operating the steering wheel 110.
In accordance with these embodiments shown in FIGS. 3 to 8, the slave 200 can be controlled not only by the output Xm of the position (angle) sensor of the master 100 but also by the output Fm of the force (torque) sensor of the master 100, as in the embodiment shown in
Thus, in case the position (angle) sensor 101 of the master 100 fails, the slave 200 can be controlled by means of the output Fm of the force (torque) sensor of the master 100.
The parallel bilateral servo control device includes a position command generating unit 600. A master force (torque) sensor output Fm and a slave force (torque) sensor output Fs are fed to a summing point (calculator) 511.
The position command generating unit 600 generates a position (angle) target value of the master 100 and the slave 200 based on the output of the summing point (calculator) 511, namely, the output Fm of the force (torque) sensor of the master 100, which is normal sensor outputs of the parallel bilateral servo control device, and the output Fs of the force (torque) sensor of the slave 200.
While in the figure the output Fm of the force (torque) sensor of the master and the output Fs of the force (torque) sensor of the slave are multiplied by a coefficient of 1.0, the value of the coefficient may be freely determined.
At the summing point (calculator) 512, the output Xs of the position (angle) sensor of the slave 200 is subtracted from the position (angle) target value generated by the position command generating unit 600 so as to calculate a deviation, which is fed to a servo controller 300. The servo controller 300 then generates a control output Ys to the slave 200 based on the deviation.
The auxiliary sensor output, namely, the output Xm of the position (angle) sensor of the master 100 is subtracted at the summing point (calculator) 513 from the position (angle) target value generated by the position command generating unit 600 so as to calculate a deviation. The deviation is fed to a servo controller 400, which then generates a control output Ym to the master 100 based on the deviation.
Furthermore, in accordance with the invention, the output Xm of the position (angle) sensor of the master 100, which is the auxiliary sensor output, is added, via a proportional calculation factor 310 based on the transfer function H(s), to the output Fm of the force (torque) sensor of the master 100, which is the normal sensor output, at a summing point (calculator) 514. The sum output is fed to the position command generating unit 600 together with the output Fs of the force (torque) sensor of the slave 200. The position command generating unit 600 then generates position (angle) target values of the master 100 and slave 200 based on the thus fed outputs.
In accordance with the above-described features of the invention, the slave 200 can be controlled not only by the output Fm of the force (torque) sensor of the master 100, which is the normal sensor output, but also by the output Xm of the position (angle) sensor of the master 200, which is the auxiliary sensor output.
Thus, the slave 200 can be controlled by the output Xm of the position (angle) sensor 101 of the master 100, which is the auxiliary sensor output, in case the force (torque) sensor 102 of the master 100, which is the normal sensor output, fails.
In this embodiment, the difference (output at a summing point 513) between the output Xm of the position (angle) sensor of the master 100, which is the auxiliary sensor output, and a control target value generated by the position command generating unit 600 is added via a proportional calculation factor 310 to the output Fm of the force (torque) sensor of the master, which is the normal sensor output, at a summing point 514. The sum is then fed to the position command generating unit 600 together with the output Fs of the force (torque) sensor of the slave 200. Based on this input, the position command generating unit 600 generates position (angle) target values of the master 100 and the slave 200.
In accordance with the embodiment shown in
Thus, the slave 200 can be controlled by the output Xm of the position (angle) sensor 102 of the master 100, which is the auxiliary sensor output, in case the force (torque) sensor 101 of the master 100, which produces the normal sensor output, fails.
In accordance with the present embodiment, the output Fm of the force (torque) sensor of the master 100, which is the auxiliary sensor output, is not always added to the output Xm of the position (angle) sensor of the master, which is the normal sensor output, but added only when more than a predetermined force (torque) is applied to the master 100.
Thus, in accordance with this embodiment, the slave is controlled by the output Fm of the force (torque) sensor of the master 100 only when the operator applied an effecting force that exceeds a predetermined level such that it is interpreted by the control system to be an emergency.
It goes without saying that the present embodiment can be applied not only to the bilateral servo control device of the type shown in
The outputs Xm of the position (angle) sensor and the output Fm of the force (torque) sensor of the master 100 represent numerical data. Therefore, if a simple majority is taken of the data, no complete agreement of values would be obtained due to sensor errors and quantization error during analog-to-digital conversion. Thus, instead of the operation to take a simple majority, an operation to take an intermediate value or an average value could be considered.
It goes without saying that the present embodiment can be similarly applied to the embodiments shown in FIGS. 3 to 9 as long as an operation is implemented in any of these embodiments whereby a majority (or an intermediate value or average value) is taken of the auxiliary sensor output value via the proportional calculator 310 and the normal sensor output.
The selection switch sel is used for selecting one of the output Xm of the master position (angle) sensor, which is the normal sensor output, and the output Fm of the master force (torque) sensor, which is the auxiliary sensor output. If the result of examination by the examination unit 320 is normal, the output Xm of the master position (angle) sensor is selected. On the other hand, if the examination unit 320 detects abnormality in the output Xm of the position (angle) sensor of the master 100, the selection switch selects the output Fm of the master force (torque) sensor.
The examination unit 320 may employ a method whereby the unit considers the output Xm of the master position (angle) sensor, which is the normal sensor output, to be normal if the value thereof is within a certain range and abnormal if it is outside such range. It may alternatively employ a method whereby redundancy is introduced into the output Xm of the master position (angle) sensor and whereby the outputs are considered to be normal if differences among them are within a certain range and abnormal if they are not within such range.
While the present embodiment involved an example of the force-feedback bilateral servo, it goes without saying that the embodiment can be similarly implemented with a parallel bilateral servo.
With reference to FIGS. 14 to 19, embodiments of the bilateral servo control device of the invention as an automobile steering control device are described.
The angular sensor 112, which detects the angle Xm of rotation of the steering wheel 110 from a center position, is provided as a means for determining the amount of rotation of the steering wheel 110 from the center position. Similarly, the torque sensor 111 for determining a torque Fm is provided as a means for determining an operation force and a reaction force applied to the steering wheel 110.
Redundancy may be introduced into the torque sensor 111 and the angular sensor 112 in the form of torque sensors 111-1 to 111-n and angular sensors 112-1 to 112-n, as shown in
The steering actuator 212 may be comprised of a known electric motor, such as a blushless motor, for example. The steering transmission mechanism 211 may be comprised of a known mechanism and is not particularly limited as long as it is capable of transmitting the motion of the steering actuator 212 to the steering wheels 210 such that the steering angle can be varied.
For example, the steering transmission mechanism 211 may be comprised of a motion conversion mechanism, such as a ball screw mechanism, for converting a rotary motion of the output shaft of the steering actuator 212 into a linear motion of the steering rod, which is not shown. The movement of the steering rod is transmitted to the steering wheels 210 via a tie rod and a knuckle arm, both of which are not shown, whereby the toe angle of the steering wheels 211 can be changed.
Alternatively, the steering transmission mechanism 211 may be comprised of a combination of a pinion gear coupled with the output shaft of the steering actuator 212 and a rack bar connected to the tie rod, instead of the ball screw mechanism.
The steering angle Xs of the steering mechanism is detected by the angular sensor 213. The torque Fs is detected by the torque sensor 214.
As shown in
The angular sensor 213 and the torque sensor 214 may be redundantly provided as angular sensors 213-1 to 213-n and torque sensors 214-1 to 214-n, as shown in
With reference to FIGS. 20 to 22, embodiments of the bilateral servo control device of the invention as an automobile brake control device are described.
A rotary motion about the motor output axis generated by the brake-driving actuator 220 is converted into a linear motion by the motion conversion mechanism 221. As a result of the linear motion conversion, the brake pad 222 is pressed against the brake disc 226, thereby producing a braking force. The position of the brake pad 222 is detected by the position sensor 227, while the pressing force is detected by the force sensor 228.
The control system for the brake-by-wire system may be based on the bilateral servo control devices shown in FIGS. 2 to 13. However, because the braking force is proportional to the pressing force of the brake pad 222, the control system preferably employs the output Fm of the force sensor of the master 100 as a control target value. In this case, too, reliability can be improved by the apparatus of the invention in which the output Xm of the position sensor is fed back to the master 100 for position feedback, as shown in
As described above, reliability of a brake-by-wire system can be improved by effectively utilizing a sensor that has originally been added for improving bilateral servo operability.
With reference to
The amount of operation of the control column or side stick 112 is detected by the position (angle) sensor 132. The force or reaction force of the control column or side stick is detected by the torque sensor 131.
The control surface 230 is driven by the driving actuator 231. The angle of rotation of the control surface 230 is detected by the angular sensor 233. The force applied to the control surface 230 is detected by the torque sensor 232.
In accordance with the above-described embodiments, the reliability of a fly-by-wire system can be improved by effectively utilizing a sensor that has originally been added for improving bilateral servo operability.
The bilateral servo control device according to the invention, which is a feedback or parallel bilateral servo control device, can be utilized for steer-by-wire or brake-by-wire systems in vehicles such as automobiles or fly-by-wire systems in aircraft, and by so doing the reliability of such systems can be improved.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/00425 | 1/20/2004 | WO | 7/19/2006 |
