Parallel dynamic simulation of multiple manipulator systems: temporal versus spatial methods

In this paper, parallel algorithms are developed for real-time dynamic simulation of a multiple manipulator system, cooperating to manipulate a large load. In an effort to achieve real-time computational rates on a general-purpose parallel system, temporal and spatial forms of parallelism are implemented to improve performance. Temporal parallelism is obtained with the use of parallel numerical integration methods. A speedup of 3.78 on four processors of a CRAY Y-MPS was achieved with a parallel four-point block predictor-corrector method for the simulation of a four manipulator system. To overcome a loss of efficiency because of a reduction in accuracy with the block integration methods, spatial parallelism is used in which the dynamics of each chain is computed simultaneously. With the same four manipulator system, this form of parallelism in conjunction with a serial integration method results in a speedup of 3.1 on four processors without the degradation in accuracy. In cases where there are more processors than chains, a new multipoint parallel integration method can still be advantageous despite the reduced accuracy. In this case, it is shown that greater effective speedups are achieved when both forms of parallelism are combined to generate more parallel tasks