Compensation Method for Lever-Arm Effect in Multi-IMU Measurement of Cable-Driven Hyperredundant Manipulators

Owing to structural design limitations, it is usually challenging to install traditional encoders or other joint measurement devices on cable-driven hyperredundant manipulators (CDHRMs). As an alternative, inertial measurement units (IMUs) can be used to measure the relative attitude of adjacent links to obtain joint information. However, the spatial offset between the IMU’s installation position and the rigid body’s center of rotation can cause a lever-arm effect, which may increase joint angle measurement errors and degrade the accuracy of the manipulator’s end-effector trajectory estimation. This article proposes a lever-arm effect compensation method for a distributed multi-IMU system to improve the accuracy of end-effector trajectory estimation. First, we establish the forward kinematics model of a hyperredundant manipulator based on the screw theory. Subsequently, the mechanism of the lever-arm effect is reanalyzed using the screw theory. Based on this mechanism and in conjunction with the kinematic model, a compensation method for the lever-arm effect in a distributed multi-IMU measurement system is proposed. Finally, we develop a pose estimation algorithm for the manipulator end-effector based on distributed IMUs, which demonstrates high effectiveness even in the presence of the lever-arm effect. The effectiveness of the proposed compensation method has been validated both through simulations and practical experiments. In the prototype experiment of the end-effector trajectory estimation task, we design and manufacture a distributed multi-IMU measurement system. The results show that, compared with the method without compensation and the conventional compensation method, the proposed method achieves higher accuracy.