Large deflection ofa compliant beam with non-uniform stiffness distribution using a PRB-3R model

Soft arms of service robots for safe manipulation, or soft legs of mobile robots for efficient locomotion have been intensively developed. The deflection of complaint beams for the soft arms or soft legs is a key criterion for design and control of robotic motions. Pseud-rigid-body (PRB) model are commonly used to predict deflection of the compliant beams with a uniform stiffness. However, soft robotic arms and legs often possess a non-uniform stiffness distribution for improving manipulation effectiveness and locomotion efficiency. In this work, a PRB-3R model is used to predict large deflections of a compliant beam with a non-uniform distribution of stiffness. By using the Euler-Bernoulli beam theory, the large deflection of a cantilever beam with a non-uniform stiffness distribution under an applied load was also derived. Results show that the PRB-3R model can precisely predict mechanical behavior of compliant beams that are not too sharp. It is not proper to apply this model to beams with very large slope. This work provides an effective design method for the soft appendages of a biomimetic robot.