Method and device for controlling walking assist device

1. A method of controlling a walking assist device, the walking assist device configured to be worn by a user, the method comprising;

determining a first state variable for a gait phase of the user based on a gait of the user;

obtaining a second state variable by smoothing and time-delaying the first state variable;

determining a torque control variable based on the gait phase in a gait cycle of the user;

obtaining a third state variable by applying the torque control variable to the second state variable; and

determining an assist torque provided by the walking assist device based on the third state variable,

wherein, in a learning mode for individualizing the walking assist device to be suitable for the user, the determining of the torque control variable comprises updating a parameter associated with controlling the assist torque to be provided by the walking assist device by selectively adjusting the torque control variable during a set gait phase of each gait cycle by (i) determining a walking assistance power index indicating an efficiency of the assist torque provided by the walking assist device to the user during a previous gait cycle and, (ii) adjusting the torque control variable associated with a current gait cycle based on the walking assistance power index, and

wherein, in a normal mode, the determining of the torque control variable comprises determining the torque control variable based on the updated parameter derived from a learning result of the learning mode of the walking assist device.

2. The method of claim 1 , further comprising:

smoothing the torque control variable to generate a smoothed torque control variable, wherein

the obtaining of the third state variable includes obtaining the third state variable by applying the smoothed torque control variable to the second state variable.

3. The method of claim 1 , wherein, in the normal mode, the determining of the torque control variable comprises:

determining a desired torque control variable by applying a state variable value corresponding to a current gait phase in the gait cycle of the user to a torque control variable determining function based on the parameter derived from the previous learning result.

4. The method of claim 1 , wherein, in the learning mode, the determining of the torque control variable comprises:

determining a retrieval torque control variable generated based on a probability function, and

setting the retrieval torque control variable as the torque control variable.

5. The method of claim 4 , wherein, in the learning mode, the determining of the torque control variable further comprises:

determining a score of a previous torque control variable based on the walking assist power index determined from a previous gait of the user; and

determining whether the score satisfies a condition.

6. The method of claim 5 , wherein

the walking assist power index includes,

a first walking assist power index indicating a magnitude of walking assist power transferred by the walking assist device, and

a second walking assist power index indicating a degree of hindrance to the user in walking by the walking assist device; and

the torque control variable is selectively adjusted based on the score by increasing the first walking assist power index in view of maintaining an absolute value of the second walking assist power index below a threshold.

7. The method of claim 6 , wherein the determining of the score comprises:

determining the score based on a weighted sum of the first walking assist power index and the second walking assist power index.

8. The method of claim 1 , wherein the determining of the first state variable comprises:

determining the first state variable based on hip joint angle information of the user measured by a sensor of the walking assist device.

9. The method of claim 1 , wherein the first state variable is a discontinuous first state variable due to noise present therein, and the obtaining of the second state variable comprises:

smoothing the first state variable by removing the noise from the discontinuous first state variable to generate a continuous first state variable; and

obtaining the second state variable by time-delaying the continuous first state variable by a time delay that varies directly with a speed or acceleration of the user.

10. The method of claim 9 , wherein the smoothing comprises:

generating the continuous first state variable based on the first state variable determined for a current gait and the first state variable determined for a previous gait.

11. A non-transitory computer-readable medium comprising computer readable instructions that, when executed by a computer, cause the computer to perform the method of claim 1 .

12. A device configured to control a walking assist device, the device comprising:

a memory; and

a controller configured to control an assist torque provided by the walking assist device based on a gait of a user wearing the walking assist device by,

determining a first state variable for a gait phase of the user based on the gait,

obtaining a second state variable by smoothing and time-delaying the first state variable,

determining a torque control variable based on the gait phase in a gait cycle of the user,

obtaining a third state variable by applying the torque control variable to the second state variable, and

determining the assist torque to be provided by the walking assist device based on the third state variable,

wherein, in a learning mode for individualizing the walking assist device to be suitable for the user, the determining of the torque control variable comprises updating a parameter associated with controlling the assist torque to be provided by the walking assist device by selectively adjusting the torque control variable during a set gait phase of each gait cycle by (i) determining a walking assistance power index indicating an efficiency of the assist torque provided by the walking assist device to the user during a previous gait cycle, and (ii) adjusting the torque control variable associated with a current gait cycle based on the walking assistance power index, and

wherein, in a normal mode, the determining of the torque control variable comprises determining the torque control variable based on the updated parameter derived from a learning result of the learning mode of the walking assist device.

13. The device of claim 12 , wherein the controller is configured to,

determine the gait phase in the gait cycle of the user based on the first state variable.

14. The device of claim 13 , wherein the controller is configured to, obtain the third state variable by,

smoothing the torque control variable to generate a smoothed torque control variable, and

applying the smoothed torque control variable to the second state variable.

15. The device of claim 13 , wherein the controller is configured to operate in the learning mode to,

determine the torque control variable,

determine a score of a previous torque control variable based on the walking assist power index determined from a previous gait of the user,

determine a retrieval torque control variable generated based on a probability function, in response to the score not satisfying a set condition, and

set the retrieval torque control variable as the torque control variable.

16. The device of claim 15 , wherein

the walking assist power index includes,

a first walking assist power index indicating a magnitude of walking assist power to be transferred by the walking assist device, and

a second walking assist power index indicating a degree of hindrance to the user in walking by the walking assist device; and

the controller is configured to adjust the torque control variable based on the score by increasing the first walking assist power index in view of maintaining an absolute value of the second walking assist power index below a threshold.

17. A walking assist device comprising:

a sensor configured to measure a gait of a user wearing the walking assist device;

a driver configured to operate an actuator of the walking assist device to provide an assist torque to the user based on a torque control signal; and

a controller configured to generate the torque control signal to control the assist torque based on the gait measured by the sensor by,

determining a first state variable for a gait phase of the user based on the gait,

obtaining a second state variable by smoothing and time-delaying the first state variable,

determining a torque control variable based on the gait phase in a gait cycle of the user,

obtaining a third state variable by applying the torque control variable to the second state variable, and

determining the assist torque provided by the walking assist device based on the third state variable,

wherein, in a learning mode for individualizing the walking assist device to be suitable for the user, the determining of the torque control variable comprises updating a parameter associated with controlling the assist torque to be provided by the walking assist device by selectively adjusting the torque control variable during a set gait phase of each gait cycle by (i) determining a walking assistance power index indicating an efficiency of the assist torque provided by the walking assist device to the user during a previous gait cycle, and (ii) adjusting the torque control variable associated with a current gait cycle based on the walking assistance power index, and

wherein, in a normal mode, the determining of the torque control variable comprises determining the torque control variable based on the updated parameter derived from a learning result of the learning mode of the walking assist device.

18. The walking assist device of claim 17 , wherein the controller is configured to determine the gait phase in the gait cycle of the user based on the first state variable.

19. The walking assist device of claim 18 , wherein the controller is configured to, obtain the third state variable by,

smoothing the torque control variable to generate a smoothed torque control variable, and

applying the smoothed torque control variable to the second state variable.