Gravity Compensation for Variable payloads using Slider-guided Compression Springs

Gravity compensation is crucial for improving the energy efficiency of robotic systems, but achieving static balancing with variable payloads remains a design challenge. This paper proposes a gravity compensation mechanism for variable payloads (GCVP), designed for static balancing of variable payloads over a full range of motion. The GCVP integrates a slider, a pair of compression springs, and an adjustable pivot pin. Variable compensation is achieved by modulating the pivot radial position inside the slider to alter the stored energy in the springs without changing their stiffness parameters. The design methodology employs the potential energy conservation and virtual work principles to formulate the spring stiffness independent of the angular position of the payload. Numerical and experimental tests were used to show the performance of the GCVP. Numerical simulations demonstrate a torque reduction of up to 98.4%. Furthermore, experimental validation under variable loading (0.5 kg to 2 kg), shows a reduction in the peak torque from 1.29 Nm to 0.16 Nm (for 0.5 kg load) and from 4.61 Nm to 0.51 Nm (for 2 kg load). Similar reductions for intermediate loads were also observed, resulting in a maximum balancing efficiency of 90.05%.