Series-Parallel Integrated Nonlinear Elastic Actuator applied to the lean motion of a bicycle simulator

2026-05-29

AI Summary

This work addresses the challenge of simultaneously achieving high torque output and high-fidelity force feedback in haptic systems by proposing a Series-Parallel Integrated Nonlinear Elastic Actuator (SPINEA). The design employs a nonlinear transmission mechanism with misaligned axes, enabling a single elastic element to function as both series and parallel elasticity without requiring clutches or additional components. This results in a compact, low-impedance actuator with high dynamic performance. By integrating nonlinear transmission, elastic coupling, and a high-precision torque control algorithm, SPINEA demonstrates exceptional performance in a bicycle simulator’s tilt actuation: it achieves a torque tracking bandwidth of 4.25 Hz under a fixed frame and maintains 4 Hz during active cycling, thereby validating its capability to deliver both high torque and high-fidelity force feedback.

Abstract

Designing robots for high-torque, high-fidelity haptic interaction is challenging. Parallel Elastic Actuators (PEAs) use elastic elements in parallel to smaller motors to complement torques, and Series Elastic Actuators (SEAs) use elastic elements in series to decouple motor impedance and improve force control. Recent work combines SEAs and PEAs to obtain both benefits but requires separate elastic elements or clutching. This paper presents the Series Parallel Integrated Nonlinear Elastic Actuator (SPINEA), which merges SEA and PEA such that a single elastic element takes on dual roles simultaneously, parallel and series. This is achieved by a nonlinear transmission in which the motor and load have misaligned rotation axes and are elastically connected. This geometry enables both high peak torque and precise torque tracking. We apply SPINEA to actuate lean of a haptic bicycle simulator, which requires high moments and precise rendering for safe and realistic rider interactions. We realized a prototype and performed experiments, both with an external excitation setup and with riders cycling. Our results confirm SPINEA's low impedance and precise torque tracking, up to 4.25 Hz with the bicycle frame fixed and up to 4 Hz with riders. The benefits may transfer to other applications requiring compact, high-performance actuation.

Problem

• haptic interaction
• high-torque actuation
• torque tracking
• bicycle simulator
• elastic actuator

Innovation

• Series-Parallel Integrated Actuator
• Nonlinear Elastic Transmission
• High-Torque Haptic Interaction
• Torque Tracking
• Bicycle Simulator