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Force regulation is an important topic in pick-and-place applications. To this end, a novel control concept for a setup consisting of two serially and co-linearly mounted axes is proposed. The position trajectory of the larger axis is tracked by a standard PD-controller. The feedback-law for the second and smaller axis mounted on the slide of the larger one is designed as an impedance control. A particular...
This study describes the design and realization of passive dynamic control for a manipulator. The control strategy is based on the idea that the shift in position and posture of an end effector attributable to an external force is regarded as the deformation of a robot. Control methods are constructed from the standard linear solid model, which describes the combination of plastic and elastic deformation...
For the purpose of enhancing compliance of robot joint, an impedance control strategy with new inner torque controller is proposed. Apparent inertia of the motor can be scaled down thanks to this new type of torque controller. Effects of different position (motor-side position θ and link-side position q) feedback strategies are explored through theoretical deviation, simulation and static stiffness...
This paper presents the result of the research about designing a device to support ankle joint by using Series Elastic Actuator (SEA). SEA is a system which consist of a DC motor, ball screw and the springs. The output force is controlled to track a trajectory which has been built before. Control force is done through control the transpose of the spring. A prototype was built to verify the possibility...
The tension control of wires can benefit from Series Elastic Actuator (SEA), which is a potential emerging actuator system. In this paper, it is verified that the tension of wires can be successfully controlled by a novel SEA, called Compact Planetary-geared Elastic Actuator (cPEA), which incorporates a planetary gear and a spring to achieve precise force sensing and compactness at the same time....
Rigid haptic devices enable humans to physically interact with virtual environments, and the range of impedances that can be safely rendered using these rigid devices is quantified by the Z-Width metric. Series elastic actuators (SEAs) similarly modulate the impedance felt by the human operator when interacting with a robotic device, and, in particular, the robot's perceived stiffness can be controlled...
Impedance control based on robust force control can improves rehabilitation therapies. In this paper, we formulate and validate a model of a series-elastic-actuator-based ankle rehabilitation device that includes a second-order description of the human joint dynamics. In order to control the output impedance of the platform we used a cascade configuration with a PD position controller as outer loop...
In this paper, a feedback controller is designed for a haptic interface using the H∞ model matching framework. The controller minimizes the H∞ norm between the haptic device-controller closed loop system and the desired virtual environment. The designed controller stably simulates high virtual spring stiffness at low sampling rate and accurately displays force feedback to the user. The model matching...
This study proposes a time-varying impedance control to smoothly stop an incoming object. The impedance dynamics are made from the Maxwell model. This system has a structure that exhibits plastic deformation. We use two types of control methods herein. Furthermore, mass, spring coefficient, and viscosity coefficient are the time-varying parameters employed to receive the incoming object without rebound...
In this study, a deformation control with spatial decoupling properties is designed and implemented. This control strategy treats the shift in position and posture attributable to an external force as the deformation of the robot. The deformation dynamics are constructed from the Maxwell and Voigt models, which describe plastic and elastic deformation, respectively. Next, a control method is proposed...
Two leading qualities of skeletal muscle that produce good performance in uncertain environments are damage tolerance and the ability to modulate impedance. For this reason, robotics researchers are greatly interested in discovering the key characteristics of muscles that give them these properties and replicating them in actuators for robotic devices. This paper describes a method to harness the...
Humanoid robots are expected to act in human environments, where some of the contacts can be non-rigid. A fairly large amount of work has been devoted to the whole-body control of humanoids under rigid contacts, but few of them take into account non-rigid contacts. Indeed, the handling of unknown compliant contacts to achieve goal directed actions and whole-body balance remains a challenge. This paper...
This paper provides an overview of the embedded joint-space control approach developed for THOR, a new series elastic humanoid. The 60 kg robot features electromechanical linear series elastic actuators (SEAs), enabling low-impedance control of each joint in the lower body via linear to rotary and parallel mechanisms. We present a distributed joint impedance control framework that leverages a custom...
As the expansion of the field of robotics has continued, the physical interaction between robots and humans has become an increasingly important area of study. Many of these physical interactions can be seen as a cooperative task conducted by both the robot and the human. Often, when two humans are interacting, one of them will act as the leader of some aspect of the task and the other will act as...
This paper is concerned with a modeling method that can be used for an experimental identification of a dynamic system. More specifically, an equivalent lumped element system is presented to represent in a unique and exact manner a complete proportional–derivative (PD) controlled servo positioning system having a flexible manipulator. The impedance and mobility approach is used to transform the P...
An arm body-building system with virtual mechanism connection is presented in this paper. Applied the cross-couple effect, proposed system will be the same as the conventional body-building mechanisms. This research includes an impedance controller and recurrent fuzzy neural networks which compensates the virtual cross-couple position error. The stability analysis and update law of the fuzzy neural...
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...
In this paper, contact dynamics of robot massage is described by the port-Hamiltonian modelling approach. In order to capture accurately the inherent characteristics of the human body in lumped-parameter manners, the conventional linear Kelvin-Voigt models are replaced by the nonlinear Hunt-Crossley models. As an application of the contact dynamics, coupled stability of compliant robotic arm with...
This paper proposes a method for designing a bilateral control system for different-sized master and slave devices with varying position and force scales. In the proposed system, the position scale that is the ratio of the slave displacement to the master one is set to be the inverse of the force scale that is the ratio of the slave force to the master one. Experimental results showed that in the...
Nonlinear elasticity of transmission is indispensable in any passively variable stiffness mechanism. However, it remains obscure how to decide a desired nonlinear force-displacement function. On the other hand biological muscular actions are associated with stiffness/impedance variation in a wide range as demanded by everyday tasks. This paper addresses the issue of designing a nonlinear elastic transmission,...
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