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In this paper we present the alpha-prototype of the WAKE-up, a wearable robotic device for the rehabilitation of locomotion of pediatric subjects with neurological diseases such as Cerebral Palsy. The WAKE-up is an active knee-ankle orthosis. It is composed of two robotic modules for the rehabilitation of knee and ankle, respectively. Each module can be utilized either alone or together with the other...
We present the design and implementation of a closed-loop control scheme for revolute joints actuated by SMA spring actuators in an antagonistic configuration. The proposed scheme employs a feedforward term, obtained as the inverse of the modified Prandtl-Ishlinskii (MPI) model of the system's response, in conjunction with angular position feedback from a joint potentiometer, to compensate for the...
General intelligent robots in daily life environment must observe and model external world, understand users' instructions and intentions. In such situations, robots always face to ambiguity of information. Conventional approaches to solve the ambiguity were using common sense database/ontology, or asking users; however developers'/users' cost is too huge. In this paper, we propose an approach in...
We present a method for the online calibration of a compact series elastic actuator installed in a modular snake robot. Calibration is achieved by using the measured motor current of the actuator's highly geared motor and a simple linear model for the spring's estimated torque. A heuristic is developed to identify operating conditions where motor current is an accurate estimator of output torque,...
Variable-stiffness actuator is a very appealing mechatronic design that combines the efficiency of stiff actuator in free space with the consistency of elastic actuation in contact. The control of such an actuation system remains a challenge due to its non-linearity and by the fact that it doubles the number of control inputs. In this paper, we propose an original control strategy to compute the whole-body...
This paper reports an experience on using the robot Lego Mindstorm NXT 2.0, model 8547, to support the teaching of Software Project Management. We conducted an experiment in which two teams developed a software project using the robot, while applying principles of project management. The experiment was divided into two parts. First, we verified the existence of related project management techniques...
Cable-driven parallel robots with flexible spring spine were present to mimic a human neck. The fixed base and moving platform of the robots are connected by cables and a compression spring. The spring serves as cervical spine to support and facilitate the motion of moving platform corresponding to human head. The cables serve as the muscles around human neck to drive the robot. The bending motion...
A feedback control to generate jumping motions for compliantly actuated multilegged robots is proposed. The method allows to specify the direction of the jumping motion. This is achieved by a constraint that defines a one-dimensional submanifold and a bang-bang control which generates a limit cycle on this submanifold. The approach is based on classical impedance control with the difference that the...
Human running motion can be modeled by a spring loaded inverted pendulum (SLIP). However, this model, despite being widely used in robotics, does not include human-like pelvic motion. In this study, we show that the pelvis actually contributes to the increase in jumping force and absorption of landing impact, both of which findings can be used to improve running robots. On the basis of the analysis...
Minimally invasive Surgery (MIS) is one of the most challenging fields for robot designers due to the limited size of the access points, to the high miniaturization level and to the dexterity needed for performing surgical tasks. For this reason, the integration of actuators should proceed in parallel with the identification of the most effective transmission mechanisms and kinematics. Conversely,...
We present a data-driven method for designing parallel compliance. Designing such compliance helps the system to improve energy efficiency, mainly by reducing negative work. The core idea is to design a controller first and then find springs working in parallel with each actuator such that force-displacement graph is lined up around displacement axis. By doing so, we simply shape the natural dynamics...
Learning complicated behaviors usually involves intensive manual tuning and expensive computational optimization because we have to solve a nonlinear Hamilton-Jacobi-Bellman (HJB) equation. Recently, Todorov proposed a class of the so-called Linearly solvable Markov Decision Process (LMDP) which converts a nonlinear HJB equation to a linear differential equation. Linearity of the simplified HJB equation...
Robots with joint elasticity find increasing interest in many research areas. A common design goal is to achieve as little mechanical joint damping as possible. To still achieve system damping often control systems are used. Here, we present a model-free approach to achieve damping via exploiting the kinetic to potential energy transformation process of the robot mass and the joint elasticity. The...
This paper presents a systematic method for experimental characterization of Bowden cable friction. A novel tension measurement method using a motion capture system and a spring is introduced. With the tension measurement method, the effects of nine variables on friction are investigated. Experimental results show that i) a combination of 7×19 FEP-coated stainless steel cable and double-sheaths has...
The design of intrinsically safe systems is an important issue in the development of physical human-robot interactions, in particular in the medical field. In this paper, we explore a new approach, motivated by a medical robotic application framework. The system is statically balanced, in any configuration. Its actuation results from a controllable modification of the balancing. This notably limits...
In this paper, we investigate the modulation of task space stiffness of mobile cable robots with elastic cables. The elasticity is introduced via springs connected in series with non-extensible cables. The benefit of such series elastic cables include tension control without using force sensors and tension redistribution. However, elasticity also reduces positioning accuracy and makes the system more...
This paper presents a Mechanically Adjustable Stiffness Actuator(MASA) for knee rehabilitation of stroke patients. The MASA is designed for safer and more effective physical human-robot interaction with patients in rehabilitation. The MASA consists of cantilever springs, a double-tripod parallel mechanism, and a torque limiter. Using the double-tripod parallel mechanism and two identical actuators,...
Synchronisation is an essential part of many controlled dynamical systems, in particular in the limb motion of legged robots. In this paper we introduce a novel control strategy that allows synchronisation of two oscillators without using any external power, but by modulating the power flow between the two oscillators. We then derive a separate energy-level controller that regulates the oscillation...
Spring-mass models have been very successful both in describing and generating running behaviors. Control of system energy within these models takes different forms, among which the use of a linear actuator in series with the leg spring has been preferred by many recent monopedal and bipedal platform designs due to its relative robustness and simplicity. However, the validity of the well-known Spring-Loaded...
The proposed research effort explores the development of active cells — simple contractile electromechanical units that can be used as the material basis for larger articulable structures. Each cell, which might be considered a “muscle unit”, consists of a contractile Nitinol SMA core with conductive terminals. Large numbers of these cells might be combined and externally powered to change phase,...
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