Victor Grosu

Estimating robot end-effector force from noisy actuator torque measurements

This paper discusses two ways to estimate the interaction force at the end-effector of a robot. The first approach that is presented combines filtered dynamic equations with a recursive least squares estimation algorithm to provide a smoothened force signal, which is useful in the (common) case of noisy torque measurements.

Mechatronic design of a sit-to-stance exoskeleton

This paper describes the design and development of an exoskeleton that can deliver assistance-as-needed to patients or elderly with muscle weakness. Since the proof-of-concept is a first step towards the development of a final commercial prototype, the design had to be adaptable for patients with different heights, be comfortable for the patients, safe in use, energy-efficient and affordable in production. For this reason a modular system was built, using the same compliant actuator system in all joints. This paper describes the global design decisions made and the construction of the actual prototype.

Design of a modular add-on compliant actuator to convert an orthosis into an assistive exoskeleton

In an ageing population many people with muscle weakness may benefit from an assisting exoskeleton to improve their mobility. Recent developments in research labs around the world are often complex, not modular and expensive. This paper introduces a novel modular compliant actuator for use in assistive lower limb exoskeletons. It is a low-cost, light-weight, compliant actuator unit that can be easily mounted on commercially available orthoses. It has the versatility to assist hip-, knee- and ankle flexion/extension individually and/or in sit-to-stance or walking activities. An adjustable passive compliance is achieved by a design based on the MACCEPA (Mechanically Adjustable Compliance and Controllable Equilibrium Position Actuator) principle. The assisting output torque and the rendered range of compliance are simulated and experimentally demonstrated.

Design of Smart Modular Variable Stiffness Actuators for Robotic-Assistive Devices

Sensors and actuators are the core components of all mechatronic systems used in a broad range of diverse applications. A relatively new and rapidly evolving area is the one of rehabilitation and assistive devices that comes to support and improve the quality of human life. Novel exoskeletons have to address many functional and cost-sensitive issues such as safety, adaptability, customization, modularity, scalability, and maintenance. Therefore, a smart variable stiffness actuator was developed. The described approach was to integrate in one modular unit a compliant actuator with all sensors and electronics required for real-time communications and control. This paper also introduces a new method to estimate and control the actuators torques without using dedicated expensive torque sensors in conditions where the actuators torsional stiffness can be adjusted by the user. A 6-degrees-of-freedom exoskeleton was assembled and tested using the technology described in this paper, and is introduced as a real-life case study for the mechatronic design, modularity, and integration of the proposed smart actuators, suitable for human–robot interaction. The advantages are discussed together with possible improvements and the possibility of extending the presented technology to other areas of mechatronics.

Learning gait by therapist demonstration for natural-like walking with the CORBYS powered orthosis

The number of mechanical degrees of freedom (DoFs) within rehabilitation robots directly influences the scope of the movements that a subject can perform when training walking. Currently, gait rehabilitation robots have a limited number of mechanical DoFs, as a consequence this limits the movements these robots can make possible. In this paper, the novel gait rehabilitation system CORBYS is presented which consists of the mobile platform and a powered orthosis which is attached to the platform. The CORBYS powered orthosis has 16 DoFs enabling more physiological movements, making it a state-of-the-art gait rehabilitation robotic system. With the sufficient number of DoFs to enable natural-like walking, the CORBYS robotic system enables the integration of the “learning gait by therapist demonstration” paradigm. This paper presents the fully integrated functional CORBYS gait rehabilitation system, with the focus on the implementation aspects which enable generation of the reference gait trajectory through learning by therapist demonstration, and the use of the generated trajectory in the robotic therapy session. The results of the initial evaluation of the robotic system obtained in tests with a selected patient are given in the paper.

Multi-Axis Force Sensor for Human–Robot Interaction Sensing in a Rehabilitation Robotic Device

Human–robot interaction sensing is a compulsory feature in modern robotic systems where direct contact or close collaboration is desired. Rehabilitation and assistive robotics are fields where interaction forces are required for both safety and increased control performance of the device with a more comfortable experience for the user. In order to provide an efficient interaction feedback between the user and rehabilitation device, high performance sensing units are demanded. This work introduces a novel design of a multi-axis force sensor dedicated for measuring pelvis interaction forces in a rehabilitation exoskeleton device. The sensor is conceived such that it has different sensitivity characteristics for the three axes of interest having also movable parts in order to allow free rotations and limit crosstalk errors. Integrated sensor electronics make it easy to acquire and process data for a real-time distributed system architecture. Two of the developed sensors are integrated and tested in a complex gait rehabilitation device for safe and compliant control.

Real-time physical layer architecture for CORBYS gait rehabilitation robot

Modern mechatronic systems present exponential evolution due to available high-end technology progress. More intelligent and more reliable systems are built, capable of sensing working environments, processing data and of autonomous decision making. Proposed Cognitive Robotic System Architecture CORBYS focuses on systems where a human is present in the robot working space and close human-robot interaction is desired. CORBYS architecture is suitable for a wide range of application areas, mentioning but not limited to, robotized vehicles, autonomous robots manipulating objects in an unstructured environment and robotic assistive devices. This work will introduce the high-levels of the architecture and describe EtherCAT based real-time physical layer for CORBYS robotic gait rehabilitation device.

Use of Compliant Actuators in Prosthetic Feet and the Design of the AMP-Foot 2.0

From robotic prostheses, to automated gait trainers, rehabilitation robots have one thing in common: they need actuation. The use of compliant actuators is currently growing in importance and has applications in a variety of robotic technologies where accurate trajectory tracking is not required like assistive technology or rehabilitation training. In this chapter, the authors presents the current state-ofthe- art in trans-tibial (TT) prosthetic devices using compliant actuation. After that, a detailed description is given of a new energy efficient below-knee prosthesis, the AMP-Foot 2.0.

Evaluation and Analysis of Push-Pull Cable Actuation System Used for Powered Orthoses

Cable-based actuation systems are preferred in rehabilitation robotics due to their adequate force transmission and the possibility of safely locating the motors away from the patient. In such applications, the cable dynamics represents the prescribing component for the system operating loads and control. A good understanding of the actuation, based on cable-conduit transmission, is therefore becoming mandatory. There are several types of cable-conduit configurations used for the actuation. Currently, there is lack of information in literature with regard to the push-pull cable type. Therefore, the main focus of this contribution is to evaluate push-pull cable-based actuation used within wearable robotic devices. This study includes working principle description of push-pull cable actuation with its characteristic advantages and drawbacks. The use of push-pull cables in bidirectional force transfer with remote actuation is investigated being integrated in a test-stand setup of a novel gait rehabilitation device. The experimental results and close analysis of the push-pull cable-based actuation system outline its performance, the overall dynamic behavior and the transmission efficiency of push-pull cables used for powered orthoses.

Torque control of a push-pull cable driven powered orthosis for the CORBYS platform

Rehabilitation robotics is a growing field which is on the verge of exploring novel actuation technologies that allows the designers to build assistive devices with large power to weight ratios without compromising the transparency of the system. In this paper a novel push-pull cable driven technology implemented in the CORBYS rehabilitation system as a solution for a proximally actuated device is presented. A novel torque control strategy enhanced with a machine learning compensation method is proposed to deal with the inherent complexities of the system. Experiments will show results obtained on the powered exoskeleton part of the platform.