Design and Study of Scissor-Mechanism-Based Pneumatic Actuator With a Characteristic of Bidirectional Contraction

A type of scissor-mechanism-based actuator with a characteristic of bidirectional contraction is designed and studied in this article. The actuator consists of soft elastomeric skin, a scissor-mechanism skeleton, and shape memory alloy (SMA) springs for tuning the contracting directions. The actuator is actuated by an air pump, and it contracts under vacuum pressure and restores under positive pressure. The two contracting directions are perpendicular to each other and can be controlled by slightly adjusting the opening angle of the skeleton actuated by SMA springs before applying the negative pressure. This bidirectional contraction characteristic enables the actuator to shorten or elongate under negative pressure. To study the bidirectional contraction characteristic of the actuator, a model to estimate the critical opening angle of the skeleton between two contracting directions is built through force analysis. Through model validation and experiments, the bidirectional contraction characteristic of the actuator is fully studied. The results show that the actuator can contract in two directions under negative pressure through controlling the opening angle as the model prediction. The new design and bidirectional contraction characteristic in this article offer valuable insight for developing novel soft actuators.