This study presents a design concept for a Full Range Gravity Balancing Mechanism (FRGBM) that utilizes an energy conservation principle to compensate for gravitational loads while enabling active stiffness modulation. The mechanism maintains equilibrium by utilizing gravitational potential energy and elastic potential energy, thereby generating restoring torques in response to link rotation. A key innovation lies in the variable-stiffness design, where the effective spring stiffness is modulated by adjusting the radial position through a control pin. This study proposes two novel mechanisms for precisely control the position of pin enabling stiffness modulation. Both designs translate rotary input into axial pin displacement, dynamically varying stiffness to accommodate changing loads. For validation of the proposed mechanism, a stiffness model is analytically de-rived based on the conservation of total potential energy, and verified through numerical simulations in MSC Adams. Simulation results demonstrate torque reduction efficiencies up to 98.1%, confirming the system’s capability to statically balance loads ranging from 5 kg to 10 kg without altering spring constants. The proposed FRGBM is highly suitable for integration into load-bearing robotic joints and assistive devices, offering tunable stiffness, compactness, and high compensation efficiency.
