Daniel Sanz-Merodio

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.

A lower-limb exoskeleton for gait assistance in quadriplegia

The potential of lower-limb exoskeletons and powered orthoses in gait assistance applications for patients with locomotive disorders would have a terrific impact in the society of the near future. This paper presents the development and main features of a lower limb exoskeleton being developed as an active orthosis to allow a quadriplegic child to walk. As the patient is not able to move any of her limbs, the device will produce her basic motions in everyday-life activities: stand up, sit down, and walk stably. Synergic biarticular actuation in the ankle, compliance controller based on the force measured by insoles at the feet and the definition of parameterized hip and foot trajectories that allow to choose the characteristics of gait are some of the new features included in this prototype. Experiments validate the improved performance of gait based on the proposed approach.

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 each state 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...

Generation and control of adaptive gaits in lower-limb exoskeletons for motion assistance

Lower-limb exoskeletons and powered orthoses in gait assistance applications for patients with locomotive disorders possess the potential to significantly affect society in the near future. This paper presents the primary features of a lower-limb exoskeleton under development as an active orthosis to enable paralysed children to walk. Because these patients are unable to move their limbs, the device generates their basic motions in everyday life, e.g. standing up, sitting down and stable ambulation. Novel features of this prototype include synergic biarticular actuation in the ankle, a compliance controller based on the force measured using insoles and the definition of parameterised hip and foot trajectories that facilitate the adaptation of gait characteristics. The improved gait performance that results from the proposed approach was experimentally validated. Graphical Abstract

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 re...

ARES, a variable stiffness actuator with embedded force sensor for the ATLAS exoskeleton

Purpose – The purpose of this study is to present a variable stiffness actuator, one of whose main features is that the compliant elements simultaneously allow measuring of the torque exerted by the joint. Conceived as a force-controlled actuator, this actuator with Adjustable Rigidity and Embedded Sensor (ARES) is intended to be implemented in the knee of the ATLAS exoskeleton for children to allow the exploitation of the intrinsic dynamic during the locomotion cycle. Design/methodology/approach – A set of simulations were performed to evaluate the behavior of the actuator mechanism and a prototype of the variable impedance actuator was incorporated into the exoskeleton’s knee and evaluations of the torque measurements capabilities along with the rigidity adjustments were made. Findings – Mass and inertia of the actuator are minimized by the compact design and the utilization of the different component for more than one utility. By a proper match of the compliance of the joint and the performed task, goo...

System identification applied to contact modeling: An experimental investigation

Many robotics applications require contact with the environment, from traditional pick and place task to legged locomotion. Nevertheless, to increase adaptability to different terrains it is necessary to know its contact properties. These properties can be known beforehand or extracted from contact forces. In this paper a practical evaluation using adaptive filtering techniques to extract the properties from different environmental conditions, with the intention to increase the adaptability of the robot to different environments is presented. We use the well-known linear spring-dashpot model and fit its parameters to four different materials in order to establish which of the reviewed methods (the recursive and windowed least squares algorithms) perform better to describe the material properties. The results show that the recursive least squares provide better tracking performance while the windowed least squares gives a smoother response.

Exploiting joint synergy for actuation in a lower‐limb active orthosis

– Lower‐limb exoskeletons and powered orthoses are external devices that assist patients with locomotive disorders to achieve correct limb movements. Current batteries cannot meet the long‐term power requirements for these devices, which operate for long periods of time. This issue has become a major challenge in the development of these portable robots. Conversely, legged locomotion in animals and humans is efficient; to emulate this behaviour, biomimetic actuation has been designed attempting to incorporate elements that resemble biological elements, such as tendons and muscles, in the mechanical systems. The purpose of this paper is to present a mechanism that resembles a human tendon to achieve and utilise the synergic actuation of the leg joints., – In this paper, we present a mechanism that resembles a human tendon to move the ankle joint and utilise the synergic actuation of hip and knee joints. Implementation of the proposed transmission system in the ATLAS active orthosis prototype allowed for a better ankle gait fit, which resulted in a more natural stride and, as expected, optimised energy consumption in the locomotion cycle and actuation energy requirements., – The fitted passive ankle motion provides toe‐off impulse, increases support force, and helps provide ground clearance., – A synergetic underactuated movement in the ankle joint, implemented by two cables in each leg, improves the functionality of the device without increasing the leg weight and while maintaining a reduced size. To achieve a correct and efficient motion in the ankle of an active orthosis, two steel cables were attached in the ATLAS orthosis. These cables act as a synergic biarticular linkage and transfer motion from the hip and knee joints. Synergic ankle motion provides impulse in the toe‐off, increases support force, and provides ground clearance. These goals are achieved with low energy expenditure because of synergical actuation, and high inertia is prevented in the more distal limb.

An Active Knee Orthosis for the Physical Therapy of Neurological Disorders

This paper presents the design of a new robotic orthotic solution aimed at improving the rehabilitation of a number of neurological disorders (Multiple Sclerosis, Post-Polio and Stroke). These neurological disorders are the most expensive for the European Health Systems, and the personalization of the therapy will contribute to a 47% cost reduction. Most orthotic devices have been evaluated as an aid to in-hospital training and rehabilitation in patients with motor disorders of various origins. The advancement of technology opens the possibility of new active orthoses able to improve function in the usual environment of the patient, providing added benefits to state-of-the-art devices in life quality. The active knee orthosis aims to serve as a basis to justify the prescription and adaptation of robotic orthoses in patients with impaired gait resulting from neurological processes.

Wearable exoskeletons for the physical treatment of children with quadriparesis

Quadriparesis, caused by a number of congenital and acquired neuropathologies, affects children with the symptoms of weakness and motor impairment in all four limbs. The physical treatment of this disease could be hypothetically improved by the use of wearable exoskeletons which would contribute to avoiding the side effects of the permanent sitting position: scoliosis, osteoporosis, spasticity, respiratory disorders, blood circulation problems, among others. Overall, the use of a wearable exoskeleton would contribute substantially to the improvement of these childrens quality of life. This paper presents the first pédiatrie wearable exoskeleton for the physical treatment of this disease. The paper shows the main components of the device and the laboratory proof of concept in two voluntary subjects.