Showing papers on "Motion planning published in 1982"

Collision-free path planning for industrial robots

Abstract: A collision-free path is a path which the robot can physically take while traveling from one location to another in an environment containing obstacles. The environment is modified by the inclusion of pseudo-obstacles which are generated by real obstacles' edges and faces; this process allows the robot itself to be represented by a point specifying its tip's location in space. An algorithm for determining the shortest distance collision-free path given a sequence of edges to be traversed has been developed for the case of stationary obstacles.

Formulation and optimization of cubic polynomial joint trajectories for mechanical manipulators

Abstract: Because of physical constraints, the optimum control of industrial robots is a difficult problem. An alternative approach is to divide the problem into two parts: optimum path planning for off-line processing followed by on-line path tracking. The path tracking can be achieved by adopting the existing approach. The path planning is done at the joint level. Cubic spline functions are used for constructing joint trajectories for mechanical manipulators. The motion of the manipulator is specified by a sequence of Cartesian knots, i.e. positions and orientations of the hand. For a 6-joint manipulator, these Cartesian knots are transformed into six sets of joint values, with each set corresponding to a joint. Piece-wise cubic polynomials are used to fit the sequence of joint values for each of the six joints. The problem is proved to be uniquely solvable. Furthermore, an algorithm is developed to schedule the time periods between each pair of adjacent knots such that the total traveling time is minimized subject to the physical constraints on joint velocities, accelerations, and jerks. FORTRAN programs have been written to implement (1) the procedure for constructing the cubic polynomial joint trajectories and (2) the algorithm for minimizing the traveling time. Results are given as an illustration.

Wa3-1 i :i 5 collision-free path planning for industr~al robots*

Abstract: A collision-free path is a path which the robot can phy- sically take while traveling from one location to another in an environment containing obstacles. The environment is modified by the inclusion of pseudo-obstacles which are gen- erated by real obstacles' edges and faces; this process allows the robot itself to be represented by a point specifying its tip's location in space. An algorithm for determining the shortest distance collision-free path given a sequence of edges to be traversed has been developed for the case of stationary obstacles. ~~~~~8-9/82/0000 -0084$00.75@1982 IEEE number and/or size of the free pascs available for path plan- ning. Lozano-Perez described linked polyhedra using swept volumes. The rotation range is then divided into a finite number of slices. Brooks adopts the idea of generalized cones (8) which are equivalent to swept volumes. Free space is then represented as overlapping generalized cones. In the methods described above, some determine the free space inside which the point robot may move freely without collisions with obstacles, while others determine the forbidden region so that a collision-free path may be traced along the boundaries of the region. This paper adopts the second approach to the problem which involves objects and obstacles that interact with a Stanford manipulator (9). The objects and obstacles are approximated by enclosing polyhe- dra. The manipulator is represented by a point; in particu- lar, the point at the tip of the end effector. As usual, its real body width is compensated for by expanding the polyhedral obstacles. The expanded polyhedra are then forbidden regions in the free space. If the point robot enters into the forbidden region, a collision will then occur. Since the third joint of the manipulator is prismatic, it creates two pseudo obstacles: one by the restriction that the front of the boom remain free of collision and the other by any confinement of the rear of the boom due to obstacles. The pseudo obstacle is not a physical object but a