Static Balancing of a Reconfigurable Linkage with Switchable Mobility by Using a Single Counterweight

Reconfigurable linkages are a special class of mechanisms that change the working topology of mechanisms during operation. This paper presents the static balancing design of a unique reconfigurable linkage by using a single counterweight. Motivated by the special requirements in lower-limb rehabilitation, the presented linkage can provide two working configurations, each having one degree of freedom (DOF) to guide the patient's lower-limb motion. A counterweight is attached to the link for eliminating the gravitational effect of the weights of patient's lower limb (as payloads) in both configurations. The novelty of this design is that the single counterweight can perfectly function in both configurations, i.e., no need to change the counterweight when the linkage configurations change. The determination of the counterweight is formulated by the linkage geometry and the weight of the payloads. An illustrative design example is demonstrated and validated via simulation software.