Design and Force/Angle Independent Control of a Bionic Mechanical Ankle Based on an Artificial Muscle Matrix

Abstract

Inspired by the natural skeletal muscles, this paper presents a novel shape memory alloy-based artificial muscle matrix (AMM) with advantages of a large output force and displacement, flexibility, and compactness. According to the composition of the AMM, we propose a matrix control strategy to achieve independent control of the output force and displacement of the AMM. Based on the kinematics simulation and experiments, we obtained the output displacement and bearing capacity of the smart digital structure (SDS) and confirmed the effectiveness of the matrix control strategy to achieve force and displacement output independently and controllably. A bionic mechanical ankle actuated by AMM was proposed to demonstrate the actuating capability of the AMM. Experimental results show that the angle and force of the bionic mechanical ankle are output independently and have a significant gradient. In addition, by using a self-sensing method (resistance self-feedback) and PD control strategy, the output angle and force of the bionic mechanical ankle can be maintained for a long time without overheating of the AMM.

Design and Position Control of a Bionic Joint Actuated by Shape Memory Alloy Wires

“…Their primary objective is to mimic the rotational motion and flexibility inherent in human and animal joints through the integration of mechanical structures, actuators, transmission methods, sensors, and controllers. Bionic joints can be categorized into several groups based on their actuators: electric motors [1,2], hydraulic actuators [3][4][5], pneumatic actuators [6][7][8], and smart material actuators (such as piezoelectric actuators [9][10][11][12], electroactive polymer actuators [13][14][15], shape memory alloy (SMA) actuators [16][17][18][19][20], and twisted and coiled polymer actuators [20,21]).…”

“…Britz et al [30] introduced a modular SMA wire rotary actuator, achieving a large rotational range through accumulated small motions from individual modules, enabled by an agonist/antagonist SMA wire configuration, and offering scalability for custom rotation and torque. Jia et al [19] implemented a series of multiple smart digital structures, constructed with SMA wires, to form an SMA artificial muscle matrix for multilevel angular control of the bionic mechanical ankle. Another way to increase the range of joint motion is by utilizing long SMA wires wrapped around multiple fixed pulleys within a limited space [31].…”