Impedance control for legged robots: an insight into the concepts involved

The application of impedance control strategies to modern legged locomotion is analyzed, paying special attention to the concepts behind its implementation which is not straightforward. In order to implement a functional impedance controller for a walking mechanism, the concepts of contact, impact, friction, and impedance have to be merged together. A literature review and a comprehensive analysis are presented compiling all these concepts along with a discussion on position-based versus force-based impedance control approaches, and a theoretical model of a robotic leg in contact with its environment is introduced. A theoretical control scheme for the legs of a general legged robot is also introduced, and some simulations results are presented

DYLEMA: Using walking robots for landmine detection and location

Detection and removal of antipersonnel landmines is an important worldwide concern. A huge number of landmines has been deployed over the last twenty years, and demining will take several more decades, even if no more mines were deployed in future. An adequate mineclearance rate can only be achieved by using new technologies such as improved sensors, efficient manipulators and mobile robots. This paper presents some basic ideas on the configuration of a mobile system for detecting and locating antipersonnel landmines efficiently and effectively. The paper describes the main features of the overall system, which consists of a sensor head that can detect certain landmine types, a manipulator to move the sensor head over large areas, a locating system based on a global-positioning system, a remote supervisor computer and a legged robot used as the subsystems’ carrier. The whole system has been configured to work in a semi-autonomous mode with a view also to robot mobility and energy efficiency.This work has been funded by the Spanish Ministry of Science and Technology under Grant CICYT DPI2001-1595 and DPI2004-05824.Peer reviewe

Articulación con rigidez controlable y dispositivo de medición de fuerza

El objeto de la invención es una articulación (1) con rigidez controlable y medición de fuerza, comprende un primer dispositivo (20), que comprende un marco (4) con una cara curva, conectado con un primer elemento motor (2), realizando este primer dispositivo (20) la regulación de la posición de la articulación (1), y un segundo dispositivo (22) que regula la rigidez de la articulación (1), que comprende un elemento de empuje (15) cuyo desplazamiento (D) determina una pre-compresión de un elemento resistivo (11) determinando de este modo la rigidez de la articulación (1), y el primer elemento motor (2) proporciona un giro al marco (4) tal que una rueda (8) del segundo dispositivo (22) recorre la cara curva del marco (4) generando una compresión (C) del elemento resistivo (11) a través de una barra de transmisión (7) asociada a dicha rueda (8) y al elemento resistivo (11)Peer reviewedConsejo Superior de Investigaciones Científicas, Universidad Politécnica de MadridB1 Patente sin examen previ

A classification of stability margins for walking robots

Throughout the history of walking robots several static and dynamic stability criteria have been defined. Nevertheless, different applications may require different stability criteria and, up to the authors’ best knowledge, there is no qualitative classification of such stability measurements. Controlling a robot gait by means of using the wrong stability criterion may prevent the task from succeeding. By the other hand, if the optimum criterion is found the robot gait can also be optimized. In this work, the stability criteria that have been applied to walking robots with at least four legs are examined attending to the stability margin on different static and dynamic situations. As a result, a qualitative classification of stability criteria for walking machines is proposed so that the proper criterion can be chosen for every desired application.Peer reviewe

Analyzing energy-efficient configurations in hexapod robots for demining applications

Purpose – Reducing energy consumption in walking robots is an issue of great importance in field applications such as humanitarian demining so as to increase mission time for a given power supply. The purpose of this paper is to address the problem of improving energy efficiency in statically stable walking machines by comparing two leg, insect and mammal, configurations on the hexapod robotic platform SILO6. Design/methodology/approach – Dynamic simulation of this hexapod is used to develop a set of rules that optimize energy expenditure in both configurations. Later, through a theoretical analysis of energy consumption and experimental measurements in the real platform SILO6, a configuration is chosen. Findings – It is widely accepted that the mammal configuration in statically stable walking machines is better for supporting high loads, while the insect configuration is considered to be better for improving mobility. However, taking into account the leg dynamics and not only the body weight, different results are obtained. In a mammal configuration, supporting body weight accounts for 5 per cent of power consumption while leg dynamics accounts for 31 per cent. Originality/value – As this paper demonstrates, the energy expended when the robot walks along a straight and horizontal line is the same for both insect and mammal configurations, while power consumption during crab walking in an insect configuration exceeds power consumption in the mammal configuration

Control architecture of the ATLAS 2020 lower-limb active orthosis

This paper outlines the control details implemented in the wearable gait exoskeleton ATLAS 2020 for improving the therapy of SMA children. This paper discusses the control challenges of a gait-training wearable exoskeleton for SMA children. Such device would also increase these children's quality of life, achieving a reduction of disability and increased functional independence.Peer reviewe

Control motion approach of a lower limb orthosis to reduce energy consumption

By analysing the dynamic principles of the human gait, an economic gait‐control analysis is performed, and passive elements are included to increase the energy efficiency in the motion control of active orthoses. Traditional orthoses use position patterns from the clinical gait analyses (CGAs) of healthy people, which are then de‐normalized and adjusted to each user. These orthoses maintain a very rigid gait, and their energy cosT is very high, reducing the autonomy of the user. First, to take advantage of the inherent dynamics of the legs, a state machine pattern with different gains in eachstate is applied to reduce the actuator energy consumption. Next, different passive elements, such as springs and brakes in the joints, are analysed to further reduce energy consumption. After an off‐line parameter optimization and a heuristic improvement with genetic algorithms, a reduction in energy consumption of 16.8% is obtained by applying a state machine control pattern, and a reduction of 18.9% is obtained by using passive elements. Finally, by combining both strategies, a more natural gait is obtained, and energy consumption is reduced by 24.6%compared with a pure CGA pattern

SILO6: A six-legged robot for humanitarian de-mining tasks

Detection and removal of antipersonnel landmines in infested fields is an important worldwide problem. Around 100 million landmines have been deployed over the last two decades, and demining will take several more decades, even if no more mines were deployed in future. A high mine-clearance rate can only be accomplished by using new technologies such as improved sensors, efficient manipulators and mobile robots. This paper presents some basic ideas on the configuration and controller of a mobile system for detecting and locating antipersonnel landmines in an efficient and effective way. The whole system has been configured to work in a semi-autonomous mode with a view also to robot mobility and energy efficiency. The paper outlines the main features of the overall system and focuses on some aspects of the controller.This work has been funded by the Spanish Ministry of Science and Technology under Grant CICYT DPI2001-1595.Peer reviewe

Identifying ground-robot impedance to improve terrain adaptability in running robots

To date, running robots are still outperformed by animals, but their dynamic behaviour can be described by the same model. This coincidence means that biomechanical studies can reveal much about the adaptability and energy efficiency of walking mechanisms. In particular, animals adjust their leg stiffness to negotiate terrains with different stiffnesses to keep the total leg-ground stiffness constant. In this work, we aim to provide one method to identify ground-robot impedance so that control can be applied to emulate the aforementioned animal behaviour. Experimental results of the method are presented, showing well-differentiated estimations on four different types of terrain. Additionally, an analysis of the convergence time is presented and compared with the contact time of humans while running, indicating that the method is suitable for use at high speeds

Andador con mecanismo de asistencia en operaciones de levantado y sentado de un usuario

Andador (1) con mecanismo de asistencia en operaciones de levantado y sentado de un usuario (21) que comprende una estructura de soporte dotada de medios de desplazamiento (2, 3), un dispositivo de sujeción (20) del usuario al andador y un sistema de bloqueo de los medios de desplazamiento, donde la estructura de soporte comprende al menos un brazo pivotante (14) que guía al dispositivo de sujeción (20) del usuario (21), un soporte guía (11) fijado al andador (1) y que guía al brazo (14) y un módulo de control (15) que controla el sistema de bloqueo de los medios de desplazamiento (2,3) y que comprende medios de selección de un modo de trabajo del andador seleccionado entre “modo andar” y “modo sentarse/levantarse”Peer reviewedConsejo Superior de Investigaciones Científicas, Universidad Politécnica de MadridB1 Patente sin examen previ