Fusion Hybrid Linear Actuator: Concept and Disturbance Resistance Evaluation

Abstract

The response of robot actuators to various dynamic interactions during contact tasks is not trivial because there exists a tradeoff between actuator-thrust force density and back-drivability. Although hybrid actuation approaches are promising, complex transmission mechanisms are necessary to synthesize forces from heterogeneous actuators. This study presents a novel concept of a fusion hybrid linear actuator to address the fundamental problems in conventional hybrid actuation approaches. The concept embodies an integrated structure of an air cylinder and a linear motor and shares the moving spaces of the piston and moving part of the linear motor inside the compact housing of the actuator. Herein, the design strategy requirements and its structural optimization processes are discussed. A kinetic friction model of a pneumatic cylinder that considers a piston structure is proposed to improve the force characteristics during dynamic interaction. Furthermore, a quantitative benchmark test is developed to maintain the contact force constant against a load actuator, to evaluate the disturbance resistance under a wide range of target contact force conditions. The concept and performance were validated by experiments comparing the proposed hybrid actuation condition with conventional pneumatic actuation conditions.

Achieving Mechanical Transparency Using Fusion Hybrid Linear Actuator for Shoulder Flexion and Extension in Exoskeleton Robot

“…The mover configuration was also optimized because the motion range of iPEHLA is limited by the permanent magnet attached to the shaft. Building upon the foundation of a previous design [13], we halved the number of permanent magnets from eight to four. This reduction was strategically chosen to expand the actuator's range of motion while still retaining adequate electromagnetic force for friction compensation.…”

“…This reduction was strategically chosen to expand the actuator's range of motion while still retaining adequate electromagnetic force for friction compensation. Since the number of magnets was halved, the electromagnetic force constant was treated as 4.0 N/A, which is half of the 8.02 N/A of the previous model [13]. Furthermore, machinewound coils were used to improve the number of turns and reduce manufacturing issues when the coils were handwound.…”

“…where F C is the Coulomb friction force, F S is the static friction force, v s is the Stribeck velocity, and σ 2 is the viscous friction coefficient. Co-authors Nakata et al [13] re-modeled the kinetic friction by considering the change in the contact force of the sealing fin on the cylinder owing to the change in the pressure in the cylinder.…”

“…The previously developed integrated pneumaticelectromagnetic hybrid linear actuator (iPEHLA) [12], which is a realization of the innovative concept of fusion hybrid linear actuator [13], outputs the base force by pneumatic force and compensates for mechanical losses using an electromagnetic force, enabling increased precision of force control. iPEHLA achieves high back-drivability by fusing two direct-drive linear actuators, that is, an air cylinder and a linear motor.…”

Actuators for Improving Robotic Arm Safety While Maintaining Performance: A Comparison Study

“…These are termed "hybrid pneumatic-electric actuators" (HPEA). A common design for an HPEA consists of a PA connected in parallel with an electric motor, as in [8][9][10][11][12]. This actuator benefits by combining the high torque provided by the PA with the fast torque response of the electric motor.…”