Concurrent layout and trajectory optimization for robot workcell toward energy-efficient and collision-free automation

The layout of robot workcell and the planned trajectory both affect safety, energy consumption and throughput of automation. However, trajectory planning and layout optimization are often studied separately in current literature, while the sequential design flow usually leads to a suboptimal solution. In this work, the location of the devices and the pose of the robot are parameterized as the homogenous transformation matrix with respect to the global frame. This enables the concurrent optimization of the layout and the trajectory under a uniform framework. For simplifying the interference and collision judgements, a cylindrical envelope is awarded to each device. The justification of interference is accomplished according to the relative position between circles, which are formed by the ground projections of envelopes. Meanwhile, by projecting the robot’s joints and envelopes of auxiliary devices both along the vertical line and onto the ground, the judgement of collision in 3D space is efficiently solved within two subspaces. Later, by relocating robots’ end-effector and joints, the deepest collided point is retreated outside the cylindrical envelope along the vertical or radial direction. And trajectory is replanned segmentally based on the relocated point. Eventually, their concurrent optimization is achieved in a cascaded flow, and the heuristic algorithm is applied to solve the problem efficiently. Experiments on an ultrasonic-peening robot workcell validate the effectiveness of the proposed method.