Abstract
In this paper, we investigate the accuracy and the computational efficiency of an IMU-based approach for solving the direct kinematics problem of parallel mechanisms with length-variable linear actuators under dynamic conditions. By avoiding to measure the linear actuators’ lengths and by using orientations instead, a comprehensive, low-cost sensor structure can be obtained that provides a unique solution for the direct kinematics problem. As a representative example, we apply our approach to the planar 3-RPR parallel mechanism, where P denotes active prismatic joints and R denotes passive revolute joints, and investigate the achievable accuracy and robustness on a specially designed experimental device. In this context, we also investigate the effect of sensor fusion on the achievable accuracy and compare our results with those obtained from linear actuators’ lengths when the Newton-Raphson algorithm is used to compute the manipulator platform’s pose iteratively. Finally, we discuss the applicability of inertial measurement units (IMUs) for solving the direct kinematics problem of parallel mechanisms.
Highlights
The direct kinematics problem of parallel mechanisms is the problem of finding the actual pose of the moveable manipulator platform with respect to the fixed base platform from the active joints’ coordinates
The planar 3-RPR parallel mechanism consists of two platforms, a fixed base platform and a moveable manipulator platform, that are connected by three identical kinematic chains consisting of passive revolute joints on the base and the manipulator platform and, between each of them, an active prismatic joint, see Figure 1
We investigate the applicability for solving the direct kinematics problem under dynamic conditions of a method, in the following referred to as linear least-squares formulation, that uses two of the linear actuators’ orientations and the orientation of the manipulator platform and provides a unique solution with each measurement, see, for example, [65]
Summary
The direct kinematics problem of parallel mechanisms is the problem of finding the actual pose of the moveable manipulator platform with respect to the fixed base platform from the active joints’ coordinates. The planar 3-RPR parallel mechanism as the planar equivalent to the Stewart-Gough platform, can only have up to six real solutions for the direct kinematics problem [12,13,14,15,16,17,18,19,20], that, cannot generally be found analytically In this context, R, U, and S denote passive revolute, universal, and spherical joints with one, two, and three degrees of freedom, respectively, and P denotes the active prismatic joints, in this paper, referred to as linear actuators.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
