Variable stiffness joint based on cylindrical cam and control method thereof

Abstract

The invention discloses a variable stiffness joint based on a cylindrical cam and a control method thereof. According to the variable stiffness joint, a cylindrical iron core electromagnet is mountedon a cylindrical cam cylinder; an annular armature is mounted on the side of a roller of a roller disc; the electromagnet generates electromagnetic attraction to the annular armature; the roller movesin a curved surface groove formed in the wall of the cylindrical cam cylinder, so that the cylindrical cam cylinder rotates and generates restoring torque; by increasing a current of an electromagnetcoil, an axial force borne by the roller disc is increased, and the joint rigidity is increased; and by reducing the current of the electromagnet coil, the axial force borne by the roller disc is reduced, and the joint rigidity is decreased. The control method of the variable stiffness joint comprises the steps of: inputting target stiffness by means of a computer; regarding a calculated actual rigidity value as a feedback signal; calculating a rigidity control value by adopting a PID control algorithm; then calculating a current value needing to be applied under the required rigidity by adopting a theoretical torsional rigidity formula; and adjusting the current to enable the joint to reach the required rigidity. Therefore, the joint and the control method achieve adjustment of the torsional rigidity of the rotational joint on the premise that a motor and an elastic element adjusting mechanism are omitted.

Description

technical field [0001] The invention relates to a variable stiffness joint based on a cylindrical cam and a control method thereof, belonging to the technical field of robots. Background technique [0002] Robots are more and more widely used in automation industry, emergency rescue, service industry, medical rehabilitation industry and other fields. However, traditional rigid drives have great human-computer interaction safety hazards in the application of service robots and rehabilitation robots. In bionic robots And the ideal torque characteristics cannot be obtained on some special robots, these defects greatly limit the robot to enter people's daily life. [0003] In recent years, in order to improve the safety of the robot in the process of human-computer interaction and adapt to the needs of different working conditions, flexible joints with variable stiffness have been designed. Ideal stiffness performance can be obtained in the workplace. [0004] At present, the ...

AI Technical Summary

Problems solved by technology

[0004] At present, the common variable stiffness joints mainly include preload control type variable stiffness joints, antagonistic variable stiffness joints, effective length control type variable stiffness joints and transmission ratio adjustable variable stiffness joints. These variable stiffness joints are controlled by motors and reducers. Driving the state change of a specific mechanical structure to adjust the joint stiffness has the disadvantages of complex structure, long response time for stiffness adjustment, and adjustment failure when the elastic element is deformed.

For example, the invention patent with the publication number CN106182067A discloses a robot flexible joint with continuously adjustable stiffness, which realizes adjustable stiffness by changing the effective length of the elastic rod with a circular section by a motor. Although its structure is relatively simple, it has low joint integration. , low space utilization, and the need for motors to participate in the shortcomings of slow response speed and inability to adjust when the elastic rod is deformed; the invention patent with the publication number of CN 104985608A discloses a flexible joint driver mechanism with adjustable stiffness. Rolling on the upper and lower cylindrical cam discs causes the axial distance between the upper and lower cylindrical cam discs to change, thereby compressing the axial spring. By adjusting the circumferential angle of the upper and lower cylindrical cam discs, the slope of the curved slope at the contact point and the pre-compression of the spring are changed. Changing the stiffness, this mechanism requires the self-locking performance of the adjusting motor to be good. Due to the introduction of the stiffness adjusting motor and the deceleration mechanism, it also has the defect of longer stiffness adjustment response time; the invention patent with the publication number of CN106737824A discloses an electromagnetic adjustable The flexible shaft joint with variable stiffness can adjust the torsional stiffness of the rotor by adjusting the electromagnetic force generated by the electromagnet on the stator, but there are problems such as the difficulty of coordinated control of multiple sets of electromagnets and the low stiffness near the equilibrium position

Images