Starting Base Position optimization in integrated task planning for mobile manipulators painting large workpieces

In order to paint large workpieces, heavy painting manipulators are always transported by mobile platforms due to their limited workspaces. To reduce the vibration of the endeffector, the base velocity of the manipulator is constant when painting. In this operation mode, the Starting Base Position (SBP) of the manipulator is important to attain the maximum manipulability and dexterity. This paper aims to optimize the SBP for painting a specified surface efficiently. An approximated decouplable model of painting manipulators is first built to get the analytically expressed inverse kinematic solutions. Then joint-level criteria for one manipulating point reflecting the manipulability and dexterity are proposed, followed by the combined criterion for a painting task about SBP with consideration of the platform velocity. Afterwards, the SBP optimization problem is translated into a least squares problem. To solve such a problem, an initial SBP value is first calculated through an algorithm based on internal penalty function method. Then a modified Levenberg-Marquardt method is employed to get the optimal SBP. Results of applications on painting a straight and an arc path indicate that the method proposed is effective and efficient.