Global energy-optimised redundancy resolution in hydraulic manipulators using dynamic programming

This paper addresses the problem of redundancy resolution in closed-loop controlled hydraulic manipulators. The problem is treated at the hydraulic level using proposed cost functions formulated into a dynamic programming approach of minimum-state representation. Bounds on joint range, actuator velocity and acceleration were enforced. This approach minimises the hydraulic energy consumption of the widely popular load-sensing and constant-supply pressure systems. The presented approach can resolve the redundancy more effectively from the hydraulic side than do actuator velocity or energy optimisation approaches, point-wise optimal approaches or some standard direct optimisation tools that may lead to inferior solutions, as shown in simulation results where up to 15–30% greater energy use is seen with some competing approaches. The results obtained motivate joint trajectory optimisation at the hydraulic level in prospective applications at construction sites where frequently driven work cycles of hydraulic construction cranes are automated.