Design And Experiments Of A Compliant Robotic Arm Based On Series Elastic Actuator

With the development of science and technology, industrial robots and service robots are facing more and more human-robot interactions, the interaction security has become a big concern. Traditional robots’body is mainly made of rigid structure in order to guarantee the performance of high speed and high precision, and the control system is based on position control mode, so the whole stiffness is quite high. Once wrong operations occur, the safety of other objects in the environment will be in threaten. In this paper, a three degrees of freedom humanoid compliant robotic arm is designed, to achieve compliant drive by introducing spring into the transmission system. Complaint interaction is realized under the compliant control approach. The main work are as follows:Imitating human arm to design and build a three degrees of freedom humanoid robotic arm named SoftArm Ⅱ, which has a roll and pitch freedom in shoulder, a pitch freedom in elbow. Designing a driving modular SEA based on linear spring which can be used in rotary joints, compliant structure is achieved by introducing compliant elements into the joints.Establishing the kinematic model, and deriving the forward kinematic solution and inverse kinematic solution, as well as the Jacobian matrix;calculating the work space of the robotic arm based on kinematic model; planing straight trajectory and circle trajectory respectively.Based on the Jacobian matrix, a system stiffness model is proposed, and the relationship between the systemic stiffness of the robotic arm and the joint stiffness is built, furthurmore the SEA spring is designed.Virtual prototype simulations are conducted using Adams, verifying the effectiveness and rationality of the proposed system stiffness model.Constructing the robotic arm control system; conducting the position following experiment and soft interaction experiments, the results shows that the robotic arm can follow the planed trajectory, and the mechanical arm had good compliance based on the SEA and force control approach. the robotic arm can avoid obstacles actively based on the end-effecter force, achieving high interaction security.