The inverse kinematics in robot manipulator have to handle the arctangent and arccosine function. However, the two functions are complicated and need much computation time so that it is difficult to be realized in the typical processing system. The purpose of this paper is to solve this problem by using Field Programmable Gate Array (FPGA) to speed up the computation power.
The Taylor series expansion method is firstly applied to transfer arctangent and arccosine function to a polynomial form. And Look-Up Table (LUT) is used to store the parameters of the polynomial form. Then the behavior of the computation algorithm is described by Very high-speed IC Hardware Description Language (VHDL) and a co-simulation using ModelSim and Simulink is applied to evaluate the correctness of the VHDL code.
The computation time of arctangent and arccosine function using by FPGA need only 320 and 420 ns, respectively, and the accuracy is <0.01°.
Fast computation in arctangent and arccosine function can speed up the motion response of the real robot system when it needs to perform the inverse kinematics function.
This is the first time such to combine the Taylor series method and LUT method in the computation the arctangent and arccosine function as well as to implement it with FPGA.
The financial support provided by Industrial Technology Research Institute (ITRI) is gratefully acknowledged.
Kung, Y.-S., Wu, M.-K., Linh Bui Thi and, H., Jung, T.-H., Lee, F.-C. and Chen, W.-C. (2014), "FPGA-based hardware implementation of arctangent and arccosine functions for the inverse kinematics of robot manipulator", Engineering Computations, Vol. 31 No. 8, pp. 1679-1690. https://doi.org/10.1108/EC-11-2012-0290
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