
Inverse Kinematics of Redundant Manipulator
Used in Tele-operation
JunjuanYang
1
,
2
, Xiulian Wang
1
, LongCui*
2
, Hongyi Li
2
1
.Shenyang Ligong University
2.State Key Laboratory of Robotics
Shenyang Institute of Automation
Chinese Academy of sciences
Shenyang, Liaoning Province, China
*Email:
cuilong@sia.cn
Abstract - To address the problem that joints would
exceed limitation in motion control of Tele-operation, a
novel efficient inverse kinematics method for the 7 DOF
manipulator of the thermonuclear fusion reactor to
trajectory planning is presented in this paper. Based on
Weighted Least-Norm (WLN) solution, the fixed joint
angle inversion method is applied to decrease the
accumulated error and avoid joint limits. Simulation
results illustrate the effectiveness of the proposed
algorithm on avoiding joint limitation and reducing the
tracking error.
Index Terms-trajectory planning; inverse kinematics;
Weighted Least-Norm solution; fixed joint angle inversion
method; avoid joint limits
I. INTRODUCTION
As people cannot clean or maintain the equipment in the
thermonuclear fusion reactor when necessary, some
manipulators are needed to handle this situation. Redundant
manipulator is a good choice because It will avoid joint limits,
singularities and obstacles when executing tasks. Redundancy
is also taken into account in control methods for velocities or
actuator torques. In this paper, we focus on avoiding the joint
limits and remaining the smoothly of joint velocities when it is
near the singularity position.
The redundancy for a particular task is generally achieved
through global or local optimization of a performance criterion
while satisfying the kinematics equations relating the end-
effector trajectory to the joint trajectory. But because of the
joints limits, the motion of the manipulator may become
singularities when the end-effector trajectory is mapped to the
joints space, reducing the flexibility of the manipulator. To
solve this problem, a Weighted Least-Norm (WLN) solution is
used in [1], while the wildly used Gradient projection method
is proposed in [2] ~ [4].
As mentioned in [5][6], there are also some iterative
methods that can solve this problems. These methods can be
applied to any kinematic structure, but they may be slower and
in some case, they may fail to work out all the possible
situations. [7] proposes an analytical methodology of 7-DOF
redundant manipulators with joint limits. An analysis is made
on the kinematics on velocity and acceleration level, showing
that the manipulators can effectively avoid the joint angle,
velocity and acceleration limits. But the calculation process is
very complicated and requires the inertial parameters of the
manipulator, limiting the usage of this method.
The configuration of the manipulator used for the
thermonuclear fusion reactor is shown in Fig.1. It will
inevitably be beyond the limits of the joint when the GPM
method is used in practical application. So in this paper, we
use the WLN method mentioned in [8]~[12] first and then
modified the approximate solution for the final track path in
an analytic way. Finally not only the complexity and amount
of calculation are reduced, but the joint limits are also
avoided.
Fig.1 the manipulator of thermonuclear fusionreactor
II. MODEL AND RELATED WORK
A. Joint models
The model of the 7 DOF manipulator used for the
thermonuclear fusion reactor is shown in Fig. 2.
Fig.2 7-DOF manipulator model
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978-1-4673-9104-7/15/$31.00 ©2015 IEEE
Proceeding of the 2015 IEEE
International Conference on Information and Automation
Lijiang, China, August 2015