We present theoretical and experimental results regarding the development and the control of a two-link robotic arm with remotized actuation via rolling diaphragm hydrostatic transmissions. We propose a dynamical model capturing the essential dynamics of the developed transmission/robot ensemble and implement a control strategy consisting of two nested loops, the inner one performing high-bandwidth joint torque regulation and the outer one producing various types of compliance responses for effective human–robot interactions. Extensive sets of experiments, testing both the low-level torque controller and the high-level compliance controller, confirm the effectiveness of the proposed hardware-software remotization architecture.

The observation of the anatomy of agile animals and their locomotion capabilities emphasizes the importance of fast and lightweight legs and confirms the intrinsic compliance integrated into muscle-tendon units as a major ingredient for energy efficient and robust locomotion. This quality is especially relevant for distal leg segments which are subject to aggressive dynamics. Legged robots are accordingly designed to improve dynamic performance by lightweight mechanisms combined with series elastic actuation systems. However, so far no designs are available that feature all characteristics of a perfect distal legged locomotion actuator such as a lightweight and low-inertia structure, with high mechanical efficiency, no stick and sliding friction, and low mechanical complexity. With this goal in mind, we propose a novel robotic leg which integrates all above features. Specifically, we develop, implement, and characterize a bioinspired robot leg that features a lightweight Series ELastic Diaphragm distal Actuator (SELDA) for active control of foot motion. We conducted experiments to compare two leg configurations, with and without foot actuation, to demonstrate the effectiveness of the proposed solution in agile forward hopping controlled by a central pattern generator. We studied how tuning SELDA's activation timing can adjust the robot's hopping height by 11% and its forward velocity by 14%, even with comparatively low power injection to the distal joint.

This paper introduces a novel hydrostatic air-liquid torque transmission system for an upper limb exoskeleton. The proposed design is based on remote electrical actuation, with grounded motors, combined with high performance fluid power transmission employed to deliver the power to the joints of the exoskeleton. The fluid transmission is based on rolling membrane cylinders that guarantee leakage-free operation, no backlash, and virtually zero stick-friction. This solution makes it possible to obtain easy controllability, good efficiency, intrinsic backdrivable operation, and reduced mass/inertia of the links of the robot. Additionally, the proposed system can be potentially implemented at relatively low-costs thanks to the employment of standard components and an architecture based on a modular approach. A test bench of the fluid transmission system is developed and a campaign of experiments is conducted to characterize its static/dynamic response for different choice of design parameters. In addition, we present a preliminary complete integrated arrangement of an upper limb exoskeleton equipped with the proposed transmission system. Results confirm the feasibility of the proposed actuation approach for the envisaged application.