Static balancing of a parallel kinematics machine with Linear-Delta architecture: theory, design and numerical investigation

• Gravity compensation of a 3-DOF spatial parallel mechanism is analytically performed.
• A feasible solution with two balancing springs and one auxiliary linkage is presented.
• Static balancing reduces the robot estimated energy requirements for common tasks.
• The compensation effectiveness is marginally affected by potential design inaccuracies.

This study deals with the compensation of gravity loads in parallel kinematics machines as a possible strategy for enhancing their working performance. In particular, the paper focuses on the static balancing of the Orthoglide 5-axis, a prototypal parallel robot with Linear-Delta architecture for machining operation. Gravity compensation is analytically carried out and a feasible design, based on tension springs and a simple additional linkage, is presented to implement the proposed strategy. Simulation results prove that the balancing device may provide an appreciable enhancement of the mechanism energy efficiency.