Abstract
This paper proposes a variable stiffness joint based on a symmetrical crank slider mechanism (SCM-VSJ). Firstly, the mechanical design and the working principle of the variable stiffness joint is described, and its stiffness regulation characteristics are studied. Secondly, the dynamical model of variable stiffness joint including joint motor, harmonic reducer and stiffness adjustment motor is established, in addition, the transmission mechanism of the crank slider mechanism and the elastic deformation of the spring bar are considered in the dynamic modeling. Finally, in order to control the dynamic stiffness of the variable stiffness joint in real time, a kind of improved PID (proportional-integral-derivative) control algorithm based on feed-forward and feedback closed-loop is proposed on the basis of the existing dynamical model, and the simulation analysis of real-time tracking control of dynamic stiffness for sinusoidal wave expected stiffness signal and random expected stiffness signal is carried out respectively. The research shows that the real-time stiffness control of SCM-VSJ can be realized effectively, and during the stiffness adjustment process, the output torque of the stiffness adjustment motor will be affected by the elastic deformation of the spring bar.
Highlights
The traditional rigid manipulator lacks enough environmental adaptability in various complex working environments, for example, in the case of human robot interaction
In the design of variable stiffness joint, the following factors should be taken into account: the joint output stiffness can change in a large range continuously, which is beneficial to improve the adaptability of the service robot to the working environment; the size of the joint should be as compact as possible and the lighter the better; the stiffness of the joint can be adjusted in real time, in some unexpected situations, the adjustment time of the stiffness is too long to guarantee the safety of human robot interaction
A variable stiffness joint SCM-VSJ based on a symmetrical crank slider mechanism is proposed
Summary
The traditional rigid manipulator lacks enough environmental adaptability in various complex working environments, for example, in the case of human robot interaction. Since the variable stiffness joint has great potential value for the future development of service robots, its mechanical design, dynamic performance, and real-time control of stiffness become the focus of research [4,5]. In the design of variable stiffness joint, the following factors should be taken into account: the joint output stiffness can change in a large range continuously, which is beneficial to improve the adaptability of the service robot to the working environment; the size of the joint should be as compact as possible and the lighter the better; the stiffness of the joint can be adjusted in real time, in some unexpected situations, the adjustment time of the stiffness is too long to guarantee the safety of human robot interaction. The summary of the research work and the prospect of the future work are given
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