For the sophisticated robotic applications such as hybrid control, tracking control, compliance control etc., a real-time interpretation of the coordinate transformation is essential to the articulated robot. In these applications, the calculation time which is required for the coordinate transformation limits the speed of robot motion.
This paper presents an algorithm which decouples the joint motion of the articulated robot manipulator into cartesian space. Each link motion can be resolved into the BRU ( Basic Resolution Unit ), $\delta$ℓ = ℓ$\delta\theta$ , where ℓ is link length and $\delta\theta$ is a resolution of the incremental encoder attached to the joint. When x- and y- plane projection of the end-point movement are expressed in $\delta$ℓ unit, projectional increments $\delta$x and $\delta$y become -1,0 or 1. Consequently the calculation with these ternary value can be executed by the simple logic rules rather than arithmetic manipulations.
For the path planning, BCU( Basic Command Unit ) can be defined. BCU is given by a single $\delta$ℓ in cartesian space. The proposed algorithm generates a manipulation signal to each joint to produce a single BCU motion in the corresponding cartesian space. A specified path can be achieved by combination of x- and y-axis BCU.
This paper demonstrates the proposed method in two-link planar robot. This method, however, can be extended into more general cases. Furthermore, since the algorithm employs one's and zero's only, hardware implementation is possible for drastic improvement of calculation speed in the real-time application.
