Inverse velocity analysis for line guidance five-axis robots

  • Authors:

  • Ming J. Tsai;Duen-Jyh Stone

  • Affiliations:

  • Department of Mechanical Engineering, National Cheng-Kung University, Tainan, Taiwan 701, Taiwan;Research Development Division, Gallant Precision Machining Co. Ltd., 5-1 Innovation 1st Road, Science Industrial Park, Hsinchu, Taiwan 300, Taiwan

  • Venue:
  • Robotics and Computer-Integrated Manufacturing
  • Year:
  • 2009

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Abstract

In this paper, inverse velocity problem for five-axis robots is investigated. The conventional method for a five-axis robot is to pseudo-inverse the 6x5 Jacobian matrix. The solution, primarily based on six freedoms inverse velocity analysis, is just an approximation with a least-square error. A five-axis robot can exactly guide an axis-symmetrical tool in 3-D space. Two exact solutions are provided for five-axis robots. One is based on the screw motion of the tool. The other is based on spherical angles of the tool to derive a 5x5 Jacobian matrix. A new type of singular configuration is discovered and is called the task singularity. The moving path of the line shaped tool is constructed as a ruled surface. Analysis of the angular acceleration shows the surface constructed based on the spherical angle representation has better characteristic. It is concluded that for five-axis robots, the tool position is better represented by five parameters rather than six parameters in order to get better solutions for inverse velocity as well as the motion planning.