Design and Experimental Verification of a Pantograph-Based Mechanism for Lower Limb Load Reduction by Compensating for Upper Body Weight

Several extant studies examine the design of power assist systems that support leg motion of the wearer. However, in most cases, actuators are always required to support the upper body weight of a wearer. This support reduces power efficiency, and thus, a new mechanism is required to effectively support upper body weight. This paper proposes a design of a lower limb load reduction device that uses a pantograph mechanism. In the mechanism, leg motion can be separated into horizontal and vertical motions, and only the lower limb load that is caused by vertical motion and the wearer’s own weight is compensated by the actuators. Additionally, the design enables support of upper body weight only in the support leg phase, and actuators are not used in the lifted leg phase. The design principle is described, and experimental results subsequently demonstrate the effectiveness of the proposed design.