US 12,214,498 B2Granted

Robot joint torque control system and load compensation method therefor

AssigneeBeijing Institute of Technology

InventorsZhangguo Yu, Qiang Huang, Yaliang Liu, Yuyu Zuo, Xuechao Chen, Gao Huang, Han Yu

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Abstract

A robot joint torque control system and a load compensation method therefor are provided, which relate to the technical field of robot joint motion control. A mathematical model of the robot joint torque control system is established first. Equivalent transformation is performed on a system functional block diagram thereof, and then it can be seen that load parameters have a great influence on joint torque output. A load compensation controller is designed to effectively eliminate the influence of the load parameters on an output torque of the joint. The system is equivalent to an inertial element on the basis of the compensation, and then a PD controller parameter is adjusted to increase an open-loop gain of the system, so as to increase a system bandwidth and increase a response speed of the joint torque control system, thereby improving performance of the joint torque control system.

A load compensation method for a robot joint torque control system, comprising accumulating a current if whose joint-end velocity is compensated for by a load compensation controller and an original current loop input instruction ir, and then using the accumulated current as a current loop input instruction of a joint torque control system to compensate for an influence of load parameters on an output torque of the joint torque control system;

wherein an output voltage Uc of a servo motor of the joint torque control system is:
Uc=Ka(ir−KIia)
where Ka is a current loop control parameter, ir is a current loop input instruction, KI is a circuit loop feedback coefficient of the servo motor, and ia is the actual accumulated current value;
the current loop input instruction ir is obtained by multiplying a joint torque error ET and a PD controller parameter KPD, and the joint torque error ET is obtained by subtracting a given torque Tr of the joint and an actual torque Tp of the joint end;
wherein voltage balance equation of the servo motor is:
U
c
=
E
+
L
⁢
di
a
dt
+
Ri
a
where E is a counter electromotive force of the servo motor, and
E
=
nK
v
⁢
d
⁢
θ
dt
,
is a reduction ratio of the gear reducer, Kv is a velocity feedback coefficient of the servo motor, θ is an actual position of the joint end,
d
⁢
θ
dt
is an actual velocity of the joint end, L is an inductance of the servo motor, and R is a resistance of the servo motor;
wherein the load compensation controller is
G
f
(
s
)
=
nK
v
K
a
,
wherein n is a reduction ratio of a gear reducer, Kv is a velocity feedback coefficient of a servo motor, and Ka is a current loop control parameter;
an open-loop transfer function of the joint torque control system is:
G
⁡
(
s
)
=
T
p
E
T
=
nK
t
⁢
K
a
⁢
K
PD
Ls
+
R
+
K
a
⁢
K
t
=
nK
t
⁢
K
a
⁢
K
PD
R
+
K
a
⁢
K
t
s
ω
+
1
=
K
a
s
ω
+
1
wherein a corner frequency of an inertial element:
ω
=
R
+
K
a
⁢
K
t
L
,
an open-loop gain
K
o
=
K
PD
⁢
nK
t
⁢
K
a
R
+
K
a
⁢
K
t
,
KPD is a PD controller parameter, Kt is a torque coefficient of the servo motor, L is an inductance of the servo motor, and R is a resistance of the servo motor.

134 more elements

Facts

Application

17/908,238Filed 9 May 2020

Priority

CN 202010186117.917 Mar 2020

Published

US 2023/0158669 A125 May 2023

Granted

4 Feb 2025

Term ends

Not estimatedThe source records don’t support an estimate.

Classification7 codes

B25J 9/1633
Characterised by the control loop: compliant, force, torque control, e.g. combined with position control
B25J 9/1638
Characterised by the control loop: compensation for arm bending/inertia, pay load weight/inertia
B25J 13/085
By means of sensing devices, e.g. viewing or touching devices: force or torque sensors
G05B 19/4155
Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to…

Abstract

Claims6