Abstract
Research on joint torque reduction in robot manipulators has received considerable attention in recent years. Minimizing the computational complexity of torque optimization and the ability to calculate the magnitude of the joint torque accurately will result in a safe operation without overloading the joint actuators. This paper presents a mechanical design for a three dimensional planar redundant manipulator with the advantage of the reduction in the number of motors needed to control the joint angle, leading to a decrease in the weight of the manipulator. Many efforts have been focused on decreasing the weight of manipulators, such as using lightweight joints design or setting the actuators at the base of the manipulator and using tendons for the transmission of power to these joints. By using the design of this paper, only three motors are needed to control any n degrees of freedom in a three dimensional planar redundant manipulator instead of n motors. Therefore this design is very effective to decrease the weight of the manipulator as well as the number of motors needed to control the manipulator. In this paper, the torque of all the joints are calculated for the proposed manipulator (with three motors) and the conventional three dimensional planar manipulator (with one motor for each degree of freedom) to show the effectiveness of the proposed manipulator for decreasing the weight of the manipulator and minimizing driving joint torques.
Highlights
For a structure of the robot manipulator one actuator can be mounted on each link to drive the link via a speed reduction unit, but actuators and speed reducers installed on the distal end become the load for actuators installed on the proximal end of a manipulator, resulting in a bulky and heavy system [1]
The work presented in this paper is based on our previous work [14], which presents a mechanical design for a three dimensional planar redundant manipulator, which guarantees to decrease the weight of the manipulator by decreasing the number of motors needed to control it
Because the inverse kinematics model gives an infinite number of solutions for a redundant manipulator, secondary performance criteria can be optimized [17], such as avoiding singular configurations and minimizing driving joint torques
Summary
For a structure of the robot manipulator one actuator can be mounted on each link to drive the link via a speed reduction unit, but actuators and speed reducers installed on the distal end become the load for actuators installed on the proximal end of a manipulator, resulting in a bulky and heavy system [1]. To show the effectiveness of the proposed manipulator in reducing the torques of its motors the inverse dynamic of the manipulator has been calculated mathematically. The work presented in this paper is based on our previous work [14], which presents a mechanical design for a three dimensional planar redundant manipulator, which guarantees to decrease the weight of the manipulator by decreasing the number of motors needed to control it. Because the inverse kinematics model gives an infinite number of solutions for a redundant manipulator, secondary performance criteria can be optimized [17], such as avoiding singular configurations and minimizing driving joint torques. The driving joint torques have been studied for the proposed manipulator for each joint and the results are compared with the results of the conventional manipulators to show the effectiveness of this manipulator for minimizing driving joint torques
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