Method and apparatus for operating a haptic system

Abstract

The present disclosure relates to a method for operating a haptic system, the haptic system comprising at least one actuator and at least one haptic control device adapted to control the at least one actuator and to provide haptic feedback to a user, the method comprising the steps of: obtaining, from a feedback computational model, modelled feedback data, obtaining, from a feedback estimator, estimated feedback data based on measurement data determined from measurement made on the haptic system, overlaying the modelled feedback data and the estimated feedback data to generate blended feedback data, and providing the blended feedback data to control the haptic feedback to the user.

Claims

1. A computer-implemented method for operating a haptic system, the haptic system comprising at least one actuator and at least one haptic control device adapted to control the at least one actuator and to provide haptic feedback to a user, the computer-implemented method comprising: obtaining, by a system comprising a processor, from a feedback computational model, modelled feedback data; obtaining, by the system, from a feedback estimator, estimated feedback data based on measurement data determined from measurement made on the haptic system; overlaying, by the system, the modelled feedback data and the estimated feedback data to generate blended feedback data; and providing, by the system, the blended feedback data to control the haptic feedback to the user by the haptic system.

2. The computer-implemented method of claim 1, further comprising: determining, by the system, reference data based on the blended feedback data; and controlling, by the system, the haptic feedback to the user in a closed-loop by using the reference data and at least a part of the measurement data as input.

3. The computer-implemented method of claim 2, further comprising: performing, by the system, an error minimization between at least the part of the measurement data and at least a part of the reference data.

4. The computer-implemented method of claim 1, wherein a ratio with which the modelled feedback data and the estimated feedback data with respective proportions are overlaid is varied.

5. The computer-implemented method of claim 4, wherein: a higher proportion of the modelled feedback data and a lower proportion of the estimated feedback data results in a less realistic haptic feedback; and a lower proportion of the modelled feedback data and a higher proportion of the estimated feedback data results in a more realistic haptic feedback.

6. The computer-implemented method of claim 1, wherein the blended feedback data is generated by use of a weighted filter.

7. The computer-implemented method of claim 6, wherein the weighted filter is a weighted sum function to which both the modelled feedback data and the estimated feedback data are applied.

8. The computer-implemented method of claim 1, wherein: the haptic system is applied to or forms a vehicle steering system, the modelled feedback data is a modelled rack force, the estimated feedback data is an estimated rack force, and the blended feedback data is a blended rack force.

9. The computer-implemented method of claim 1, wherein the measurement data comprises at least one of: a measured pinion angle, a measured pinion speed, an applied actuator torque or an applied pinion torque.

10. An apparatus for operating a haptic system, the haptic system comprising at least one actuator and at least one haptic control device adapted to control the at least one actuator and to provide haptic feedback to a user, the apparatus comprising: a processing unit configured to: obtain from a feedback computational model, modelled feedback data; obtain from a feedback estimator, estimated feedback data based on measurement data determined from measurement made on the haptic system; overlay the modelled feedback data and the estimated feedback data to generate blended feedback data; and provide the blended feedback data to control the haptic feedback to the user by the haptic system.

11. The apparatus of claim 10, wherein the haptic system is at least part of a vehicle steering system.

12. The apparatus of claim 10, wherein the haptic system further comprises a rack and a pinion; and the processing unit is further configured to determine reference data based on the blended feedback data, wherein the reference data comprises at least one of a reference pinion torque or a reference pinion angle.

13. A vehicle steering system, comprising: at least one actuator, at least one haptic control device adapted to control the at least one actuator, and an apparatus for operating the vehicle steering system, wherein the apparatus comprises: a processing unit configured to: obtain from a feedback computational model, modelled feedback data; obtain from a feedback estimator, estimated feedback data based on measurement data determined from measurement made by the at least one haptic control device; overlay the modelled feedback data and the estimated feedback data to generate blended feedback data; and provide the blended feedback data to control, via the at least one haptic control device, haptic feedback by the at least one actuator.

14. A haptic device, comprising: a processor; and a memory, coupled to the processor, that stores executable instructions that, when executed by the processor, facilitate performance of operations, comprising: obtaining from a feedback computational model, modelled feedback data; obtaining estimated feedback data based on measurement data determined from measurement made by the haptic device; overlaying the modelled feedback data and the estimated feedback data to generate blended feedback data; and controlling haptic feedback by the haptic device based on the blended feedback data.

15. A non-transitory computer readable medium having instructions stored thereon that, in response to execution, cause a system comprising a processor to perform operations comprising: obtain, from a feedback computational model, modelled feedback data; obtain, from a feedback estimator, estimated feedback data based on measurement data determined from measurement made on a haptic system; overlay the modelled feedback data and the estimated feedback data to generate blended feedback data; and provide the blended feedback data to control haptic feedback by the haptic system.

16. The non-transitory computer readable medium of claim 15, wherein the operations further comprise: determine reference data based on the blended feedback data; and control the haptic feedback in a closed-loop by using the reference data and at least a part of the measurement data as input.

17. The non-transitory computer readable medium of claim 16, wherein the operations further comprise: perform an error minimization between at least the part of the measurement data and at least a part of the reference data.

18. The non-transitory computer readable medium of claim 15, wherein a ratio with which the modelled feedback data and the estimated feedback data with respective proportions are overlaid is varied.

19. The non-transitory computer readable medium of claim 15, wherein the blended feedback data is generated by use of a weighted filter.

20. The non-transitory computer readable medium of claim 19, wherein the weighted filter is a weighted sum function to which both the modelled feedback data and the estimated feedback data are applied.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Exemplary embodiments of the invention will be described in the following with reference to the following drawings.

(2) FIG. 1A shows an illustration of an example of a haptic system according to an embodiment,

(3) FIG. 1B shows an illustration of another example of a haptic system according to an embodiment,

(4) FIG. 2 shows in a block diagram a closed-loop feedback control method to be applied to a haptic system,

(5) FIG. 3 shows in a block diagram a closed-loop feedback control reference architecture to be applied to a haptic system,

(6) FIG. 4 shows in a block diagram a closed-loop feedback control reference architecture to be applied to a haptic system, and

(7) FIG. 5 shows in a flow chart a method for operating a haptic system according to an embodiment.

(8) The figures are merely schematic representations and serve only to illustrate embodiments of the invention. Identical or equivalent elements are in principle provided with the same reference signs.

DESCRIPTION OF EMBODIMENTS

(9) FIGS. 1A and 1B each show, by way of example, a haptic system 100, which is provided here as a vehicle steering system or a part thereof. Of course, the haptic system 100 may also be provided as or may comprise an exoskeleton, a joystick, or the like. The haptic system 100 comprises at least one actuator 110, which is formed here as an electric motor, a haptic control device 120, which is adapted to control the at least one actuator 110 and formed here as a steering wheel, a data processing unit 130, which is adapted to control feedback to the haptic control device 120, and a feedback actuator 140 (see FIG. 1B), which is adapted to generate a feedback to the haptic control device 120, wherein the feedback comprises at least one of a force, a torque, vibration, etc. In the embodiment according to FIG. 1A, the feedback actuator 140 is built-in in the actuator 110, which is here an Electric Power Assisted Steering (EPAS) motor. In the embodiment according to FIG. 1B, the feedback actuator 140 is formed as a separate electric motor that is functionally coupled to the haptic control device 120.

(10) The haptic system 100 as shown in FIGS. 1A and 1B further comprises a torsion bar 150, and a rack and pinion 160. From a functional perspective, this allows the actuator 110 that drives the rack and pinion 160 to be operated by manipulating the haptic control device 120, in order to adjust the steering angle of the wheels of a vehicle and steer the vehicle.

(11) FIG. 2 shows in a block diagram a closed-loop feedback control method, which may be applied to the above haptic system 100 and may be carried out by the data processing unit 130. The block diagram comprises a first block B1 adapted to obtain and process several input data In1, e.g. input signals, and to provide first output data Out1, e.g. output signals. The input data In1 comprises one or more of a measured pinion angle, a measured pinion speed, a measured vehicle speed, an applied motor torque, and a measured pinion torque. The first output data Out1 may be a reference pinion torque or a reference angular position, such as a pinion angle. Downstream to the first block B1 the block diagram further comprises a summation point SP to which the first output data Out1 are provided. The block diagram further comprises a pick-up point PP, where at least one of the input data In1 is picked-up for a feedback provided to the summation point SP. For example, the picked-up input data In1 may be the measured pinion torque or the measured pinion angle, depending on the reference that is to be provided. Accordingly, if the output data Out1 is a reference pinion torque, the picked-up input data In1 is the measured pinion torque, and if the output data Out1 is a reference pinion angle, the picked-up input data In1 is the measured pinion angle. The block diagram further comprises a second Block B2 adapted to obtain the result of the summation point SP. For example, the second Block B2 may be a feedback controller, adapted to perform error minimization between the input data In1, which is measurement data obtained from measurements directly made on the haptic system 100, and the output data Out1, which is the reference data determined by block B1. Block B2 provides output data Out2, which is e.g. a motor torque request that may be provided to e.g. the feedback actuator 140 in order to drive the feedback on the haptic control device 120.

(12) FIGS. 3 and 4 each show in a block diagram a closed-loop control reference architecture according to a respective embodiment. The two architectures differ from each other mainly in that FIG. 3 shows an architecture for providing a torque reference and FIG. 4 shows an architecture for providing a position reference. Referring to FIG. 2, the respective closed-loop control reference architecture forms or is comprised by block B1 as designated in FIG. 2, so that the output data of the respective closed-loop control reference architecture corresponds to the output data Out1 as designated in FIG. 2.

(13) Now referring to FIG. 3, the closed-loop control reference architecture comprises several blocks B1-1 to B1-7, and a summation point SP-B1. Block B1-1 represents a feedback computational model adapted to determine, compute, calculate, generate, etc. and output modelled feedback data OutB1-1, which modelled feedback data here is a modelled rack force. The modelled feedback data OutB1-1 may also be referred to as “virtual” steering feedback data, since the forces are rather hypothetical as these are computed by using a suitable computational model. The feedback computational model B1-1 receives a number of input data, e.g. a measured vehicle speed and a measured pinion angle. The model may at least partly describe the haptic system 100 by using mathematical and/or physical concepts, formulas and/or language, in order to make predictions about the system behavior.

(14) Block B1-2 represents a feedback estimator adapted to determine, compute, calculate, generate, etc. and output estimated feedback data OutB1-2 based on measurement data determined from measurement made on the haptic system 100. The estimated feedback data OutB1-2 here is a estimated rack force, wherein the estimate may also be referred to as a calculation, or the like, and in the best case—if the estimation is accurate—may correspond to the actual rack force. There may be one or more further outputs from Block B1-2, which are not explicitly designated here, such as an estimated rack acceleration, or the like.

(15) Block B1-3 represents a feedback data overlay adapted to overlay the modelled feedback data OutB1-1 and the estimated feedback data OutB1-2 to generate blended feedback data OutB1-3, which is here a blended rack force. Accordingly, the input data of the feedback data overlay B1-3 is the modelled feedback data OutB1-1 and the estimated feedback data OutB1-2. The feedback data overlay may be based on weighted filtering and may use e.g. a weighted sum of the modelled feedback data OutB1-1 and the estimated feedback data OutB1-2. The blended feedback data OutB1-3 is used to control the haptic feedback to the user, which is at least primarily based on the output data Out1, which is here a reference pinion torque. The blended feedback data OutB1-3 is fed to summation point SP-B1.

(16) Blocks B1-4 to B1-6 represent some system variables that may be taken into account in addition to the blended feedback data OutB1-3 and are therefore also fed to the summation point SP-B1. For example, blocks B1-4 to B1-6 may be associated with an active friction force, e.g. a rack friction force F.sub.rack,fric, an active damping force, e.g. a rack damping force F.sub.rack,damp, and an active inertia force, e.g. a rack inertia force F.sub.rack,inert, or the like. It is noted that block B1-4 receives the estimated rack acceleration from block B1-2 as input data. The sum of the several forces of the system forms the total force, e.g. the total rack force.

(17) Block B1-7 represents an inversion function.

(18) For example, the output data Out1, which represents the reference data used in the closed-loop feedback control method according to FIG. 2, may be expressed by the following equation of motion (equation 1):
F.sub.rack,tot=m.sub.ref{umlaut over (x)}+b.sub.ref{dot over (x)}+F.sub.rack,fric+F.sub.rack,eff=F.sub.rack,inert+F.sub.rack,damp+F.sub.rack,fric+F.sub.rack,vir(1W.sub.f)+F.sub.rack,estW.sub.f,
wherein F.sub.rack,tot is the total rack force, F.sub.rack,inert is the output of block B1-4, F.sub.rack,damp is the output of block B1-5, F.sub.rack,fric is the output of block B1-6, W.sub.f is a weighted sum of the modelled feedback data OutB1-1 and the estimated feedback data OutB1-2.

(19) For example, the output data Out1, which is here a reference pinion torque, may be expressed by the following equation (equation 2):
M.sub.pin,ref=K.sup.−(F.sub.rack,tot),
wherein M.sub.pin,ref is the output data Out1 and K.sup.−1 is the inversion function provided by block B1-7. Accordingly, the reference torque is finally computed by the inverse of a basic assist function, K.sup.−1, which is already an existing function that relates to F.sub.rack,tot and M.sub.pin,ref. Basically, it may mean how much driver torque should be applied for a given force on the steering rack in general.

(20) The above force overlay approach may be used to control the feedback to the user, e.g. the driver of a vehicle. For example, if a vehicle is driving on a rough road and the actual road disturbances are not to be felt, W.sub.f may be set to W.sub.f=0. As a result, there is only a virtual steering feedback with no actual road response for a comfortable steering feel. On the contrary, if the vehicle is driving with high speed, for a safety critical maneuver, W.sub.f may be set to W.sub.f=1, in order to emphasize on the realistic road condition for a faster driver response and/or a lower reaction time to feel the actual vehicle behavior.

(21) Now referring to FIG. 4, another example of the closed-loop control reference architecture will be described. Basically, this closed-loop control reference architecture comprises the same or at least similar blocks B1-1 to B1-6, which will therefore not be described here again. One difference between the architectures of FIG. 3 and FIG. 4 is that in the architecture according to FIG. 4, the output data Out1 is a reference pinion position, and particularly a reference pinion angle. Therefore, block B1-7 can be omitted. As explained above, the total steering rack force F.sub.rack,tot for the steering system is the sum of different force components: inertial force F.sub.rack,inert, damping force F.sub.rack,damp, Coulomb friction force F.sub.rack,fric and external forces coming from the vehicle tires. Using the same equation as explained above in equation 1, and rearranging it gives a second order differential equation, which can be expressed as (equation 3):
m.sub.ref{umlaut over (x)}=−b.sub.ref{dot over (x)}−F.sub.rack,vir+(F.sub.rack,vir−F.sub.rack,est)W.sub.f−F.sub.rack,fric+F.sub.rack,tot=−b.sub.ref{dot over (x)}−F.sub.rack,vir+F.sub.rack,effW.sub.f−F.sub.rack,fricK(M.sub.pin)=−b.sub.ref{dot over (x)}+F.sub.rack,dyn,
and can be further expressed as (equation 4):

(22) ${\stackrel{.Math.}{\theta }}_{\mathrm{pin},\mathrm{ref}}=\frac{1}{i_{\mathrm{rp}}}\stackrel{.Math.}{x}=\frac{1}{i_{\mathrm{rp}}}\left(-\frac{b_{\mathrm{ref}}}{m_{\mathrm{ref}}}\stackrel{.}{x}+\frac{1}{m_{\mathrm{ref}}}{F}_{\mathrm{rack},\mathrm{dyn}}\right),$
wherein equation 4 is a conversion from rack position (or acceleration) variable to pinion angle (or acceleration) variable via the steering rack to pinion gear ratio i.sub.rp. This results in a position based reference which is mathematically equivalent to a torque control reference, where, however, the causality is basically inverted due to their respective definitions. Again, there would not be any actual road feedback with W.sub.f=0 and the virtual rack force model provides a virtual steering feedback. Whereas with W.sub.f=1, the entire estimated ‘actual’ rack force is bypassed with no virtual rack force, to realize the realistic road condition.

(23) Referring now to FIG. 5, which shows a flow chart, a method for operating the haptic system 100 will be described in the following.

(24) In a step S1, modelled feedback data is obtained from the feedback computational model, which is represented by block B1-1 as shown in FIGS. 3 and 4. In a step S2, estimated feedback data based on measurement data determined from measurement made on the haptic system 100 is obtained from the feedback estimator, which is represented by block B1-2 as shown in FIGS. 3 and 4. In a step S3, the modelled feedback data and the estimated feedback data to generate blended feedback data are overlayed, e.g. by block B1-3. In a step S4, the blended feedback data OutB1-1 is provided to control the haptic feedback to the user.

(25) Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from the study of the drawings, the disclosure, and the appended claims. In the claims the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items or steps recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope of the claims.

LIST OF REFERENCE SIGNS

(26) 100 haptic system (e.g. vehicle steering system etc.) 110 actuator 120 haptic control device 130 data processing unit 140 feedback actuator 150 torsion bar 160 rack and pinion