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Biped robot may become unstable during dynamic walking because of the huge impact/contact forces produced by foot instant landing. In this paper, force/torque-based compliance control is applied to absorb the impact forces generated between the contacting foot and the ground to keep stable dynamic walking. By imitating human's muscles to absorb the landing force, this method models the ground and...
Crane systems used during offshore installations in harsh sea conditions must satisfy rigorous requirements in terms of safety and efficiency. The vertical vessel motion which is due to ocean waves excites dynamic forces which have an extensive effect on the overall crane structure and its lifetime. Furthermore, the operator gets handicapped during fine positioning of the payload. Thus, compensation...
This article presents the experimental verification of kinematic and dynamic models of the PHANToM Premium 1.0 haptic device. Dynamic properties are evaluated, in order to apply nonlinear control techniques and evaluation of manipulability and energy in real-time. Position kinematics and differential kinematics are validated for the trajectory planning by using joint control techniques for local haptic...
The article presents the inverse dynamics model of a 6-Universal-Prismatic-Spherical (UPS) parallel mechanism and proposes the structure of a force controller for the execution of tasks characterized by interaction with the environment. The task space model of machine's dynamics is obtained in an efficient and compact form by means of the principle of virtual work. A simulation is shown that hybrid...
To get compact instruments in robot-assisted minimally invasive surgery (MIS), each servo motor was installed the base and motor torque was transmitted to each joint through a tendon-pulley system. Trajectory tracking control is very important in MIS. In this paper, dynamic structure and equation of motion including the effect of rotor inertia for a class of 3-dof tendon-driven minimally invasive...
We propose a new motion dynamics approach to solve the PnP problem, where a dynamic simulation system is constituted by springs and balls. The equivalence between minimizing the energy of the dynamic system and solving the PnP problem is proved. With the assumption of the existence of resistances, the solution of the original PnP problem can be solved through the simulation of the process of the movement...
In this paper, the neural impedance controller is formulated to regulate the contact force with the environment. When robot uncertainties are present, the performance of the impedance controller is degraded. To compensate for uncertainties in both robot dynamics and environment, neural network is introduced at the desired trajectory. The training signal is defined to satisfy the desired goal. This...
A new hierarchical closed loop fuzzy control system for horizontal plane trajectory tracking of underactuated Autonomous Underwater Vehicles (AUV) is presented. A model for the AUV is formulated introducing a polar coordinates transformation for the velocities in the body fixed frame. It is employed to control the unactuated sway direction, the longitudinal position and the yaw by using the surge...
Most differential drive platforms are equipped with two independent motors and casters. Possible misalignment between the platform direction and caster orientations and the unbalanced motor dynamics are some of the factors that make it difficult to properly drive the platforms. We present an adaptive nonlinear controller system that reduces the effect of disturbances on the platform motion. The controller...
Control of relative position and orientation are usually split into two parts in rendezvous and docking missions. It is simple but not precise enough. Based on dual number, this paper derives coupled dynamics equations of two spacecrafts in which the coupling effect of relative position and orientation is indicated. Furthermore, an incremental PID control law is designed to control the coupled system...
An analytical-numerical method based on solution of inverse dynamics is presented for determining the load workspace of generally configured parallel motion systems with up to 6 degrees of freedom. The kinematic workspace is also obtained by the method, since the solution of inverse kinematics is embedded in the procedure. The method is first developed for 3DoF motion systems to take the advantages...
In the paper we evaluate two learning methods applied to the ball-in-a-cup game. The first approach is based on imitation learning. The captured trajectory was encoded with Dynamic motion primitives (DMP). The DMP approach allows simple adaptation of the demonstrated trajectory to the robot dynamics. In the second approach, we use reinforcement learning, which allows learning without any previous...
Most industrial robots nowadays still employ strategies that neglect or minimize the effects of task dynamics. Some tasks, however, are intrinsically dynamic and can only be accomplished by considering their dynamic aspects. We address ball catching as a prominent and widely studied example for such a task. The paper follows a special approach to accomplish the task: the nonprehensile catching, which...
In this paper, we consider the force/position tracking problem for a robot in compliant contact with a kinematically known planar surface. We propose a novel controller that achieves predefined performance indices regarding the transient and steady state response of the robot force/position tracking errors and ensures no loss of contact of the robot-end effector. The proposed controller is model free...
In state of the art robotics, high positioning accuracy is achieved by using solid and stiff components as well as powerful drive units which have no backlash. In contrast, human beings are able to achieve remarkable high positioning accuracy despite of low mass, low power consumption and relatively simple mechanics. One approach to obtain this accuracy is to temporarily create additional supporting...
The paper focuses on hyper-redundant arms with continuum elements that perform the grasping function by coiling. First, there is concern with the dynamic model of the continuum arm for the position control during non-contact operations with the environment. A frequency stability criterion based on the Kahman - Yakubovich - Popov Lemma and P and PD control algorithms is proposed. Then, the grasping...
We examine time-optimal straight-line trajectory generation for three-wheeled omni-directional mobile robots. Our studies are based on the mobile robot dynamics with battery voltage bounds. We formulate a multi-objective problem that has both translational and rotational costs for time-optimality. Using the switching functions by maximum principle, we present a new approach to determine extreme control...
This paper presents the control architecture and preliminary experimental results of a high performance parallel robot used for ankle rehabilitation. The goal of this work was to design suitable control algorithms for diagnostic, training and rehabilitation of the ankle in presence of musculoskeletal injuries. A position control scheme is used for patient-passive exercises while an admittance control...
Considering slowly varying environmental external disturbances and their uncertainties, an adaptive nonlinear PID controller for the dynamic positioning system of ships is designed based on vectorial backstepping with integrator under unknown constant environmental disturbances. Using Lyapunov stability theory, it is proved that the resulting dynamic positioning control system of ships is uniformly...
A nonlinear output feedback controller is developed for an Underactuated manipulator in this paper. The PPR planar Underactuated manipulator consists of two active joints and one passive joint. The dynamic constraint on the free link is 2nd-order non-holonomic. Firstly, the motion equations are transformed into a special form using some global coordinate and input transformations. Secondly, a time-varying...
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