Human muscular strength amplification robot driven by intention of user and driving method thereof
A muscular strength enhancing robot to be driven by an intention of a user and a method of driving the robot are disclosed. The robot includes an actuator attached to a portion of a body of the user and configured to be actuated by enhancing a muscular strength, an encoder connected to the actuator and configured to measure an actual velocity at which the actuator moves, a force or torque sensor configured to measure an intensity of a force to be applied, an admittance modeling module configured to calculate a target velocity using the intensity of the force, and a proportional integral derivative (PID) control module configured to control actuation of the actuator in proportion to a velocity difference between the target velocity and the actual velocity, control the actuation by a cumulative value of the velocity difference, and control the actuation by a difference between a previous and a current velocity difference.
1. A muscular strength enhancing robot to be driven based on an intention of a user, the robot comprising:
an actuator attached to a portion of a body of the user and configured to be actuated by enhancing a muscular strength in a movement direction in which the portion moves;
an encoder connected to the actuator and configured to measure an actual velocity v r at which the actuator moves in the movement direction;
a force or torque sensor configured to measure an intensity of a force f h to be applied in the movement direction;
an admittance modeling module configured to calculate a target velocity v d using the intensity of the force f h measured by the force and torque sensor;
a proportional integral derivative (PID) control module configured to control actuation of the actuator in proportion to a velocity difference v e between the target velocity v d calculated by the admittance modeling module and the actual velocity v r measured by the encoder, control the actuation of the actuator by a cumulative value of the velocity difference v e , and control the actuation of the actuator by a difference between a previous velocity difference v e and a current velocity difference v e ;
an input energy calculating module configured to calculate a current input energy E in (k) of the robot;
an output energy calculating module configured to calculate a current output energy E out (k) of the robot; and
a passivity control module configured to determine stability of a system of the robot by comparing the calculated current input energy E in (k) to the calculated current output energy E out (k), and calculate a damping element β and apply the calculated damping element β to the actuator in response to a determination that the system is unstable.
2. The robot of claim 1 , wherein the input energy calculating module is configured to calculate the current input energy E in (k) by calculating an instantaneous input energy using the force f h measured by the force or torque sensor and the target velocity v d calculated by the admittance modeling module, and adding the calculated instantaneous input energy and a previous input energy.
3. The robot of claim 2 , wherein the current input energy E in (k) is calculated based on the following Equation,
E
in
(
k
)
=
{
E
in
(
k
-
1
)
+
Δ
T
(
f
h
(
k
)
·
v
d
(
k
)
)
,
if
f
h
(
k
)
·
v
d
>
0
E
in
(
k
-
1
)
,
if
f
h
(
k
)
·
v
d
(
k
)
≤
0
[
Equation
]
wherein “ΔT” denotes a sampling time.
4. The robot of claim 1 , wherein the output energy calculating module is configured to calculate the current output energy E out (k) by calculating an instantaneous output energy using a force f c of controlling the actuation of the actuator by the PID control module and the target velocity v d calculated by the admittance modeling module, and adding the calculated instantaneous output energy and a previous output energy.
5. The robot of claim 4 , wherein the current output energy E out (k) is calculated based on the following Equation,
E
out
(
k
)
=
{
E
out
(
k
-
1
)
+
Δ
T
(
f
c
(
k
)
·
v
d
(
k
)
)
,
if
f
c
(
k
)
·
v
d
>
0
E
out
(
k
-
1
)
,
if
f
c
(
k
)
·
v
d
(
k
)
≤
0
[
Equation
]
wherein “ΔT” denotes a sampling time.
6. The robot of claim 4 , wherein the passivity control module is configured to calculate the damping element β based on the following Equation,
β
(
k
)
=
{
-
E
obs
(
k
)
(
f
c
)
2
Δ
T
,
if
E
obs
<
0
and
f
c
≠
0
0
,
if
E
obs
≥
0
or
f
c
=
0
[
Equation
]
wherein “E obs (k)” is a value obtained by subtracting a value of E out (k) from a value of E in (k), E in (k)−E out (k), and “ΔT” denotes a sampling time.
7. A method of driving a muscular strength enhancing robot based on an intention of a user, the method comprising:
measuring, by an encoder connected to an actuator, an actual velocity v r at which the actuator moves in a movement direction in which a portion of a body of the user to which the actuator is attached moves;
measuring, by a force or torque sensor, an intensity of a force f h to be applied in the movement direction;
calculating, by an admittance modeling module, a target velocity v d using the intensity of the force f h measured by the force or torque sensor;
controlling actuation of the actuator in proportion to a velocity difference v e between the target velocity v d calculated by the admittance modeling module and the actual velocity v r measured by the encoder, controlling the actuation of the actuator by a cumulative value of the velocity difference v e , and controlling the actuation of the actuator by a difference between a previous velocity difference v e and a current velocity difference v e , by a proportional integral derivative (PID) control module;
calculating, by an input energy calculating module, a current input energy E in (k) of the robot;
calculating, by an output energy calculating module, a current output energy E out (k).of the robot; and
determining, by a passivity control module, stability of a system of the robot by comparing the calculated current input energy E in (k) to the calculated current output energy E out (k); and
calculating a damping element β and applying the calculated damping element β to the actuator in response to a determination that the system is unstable, by the passivity control module.
8. The method of claim 7 , wherein the calculating of the current input energy E in (k) comprises:
calculating the current input energy E in (k) by calculating an instantaneous input energy using the force f h measured by the force or torque sensor and the target velocity v d calculated by the admittance modeling module, and adding the calculated instantaneous input energy and a previous input energy.
9. The method of claim 7 , wherein the calculating of the current output energy E out (k) comprises:
calculating the current output energy E out (k) by calculating an instantaneous output energy using a force f c of controlling the actuation of the actuator by the PID control module and the target velocity v d calculated by the admittance modeling module, and adding the calculated instantaneous output energy and a previous output energy.
10. The method of claim 8 , wherein, in response to the determination that the system is unstable, the calculating of the damping element β and the applying of the calculated damping element β to the actuator by the passivity control module comprises:
calculating the damping element β based on the following Equation,
β
(
k
)
=
{
-
E
obs
(
k
)
(
f
c
)
2
Δ
T
,
if
E
obs
<
0
and
f
c
≠
0
0
,
if
E
obs
≥
0
or
f
c
=
0
[
Equation
]
wherein “E obs (k)” is a value obtained by subtracting a value of E out (k) from a value of E in (k), E in (k)−E out (k), and “ΔT” denotes a sampling time.