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Precise force control and position control is essential for many robotic applications. During unilateral or bilateral object handling remote applications, human operators apply excess forces on the actuators with the intention of better grip and it is possible to damage the handled objects. This paper proposes position control and force control techniques when human applies excess force. The controllers...
In contrast to precise position control of the robot arms and manipulators, the force control has been studied recently. The robust position control does not allow the robots to share the same space with humans because the robots faithfully follow the position command, and it may lead to break the contacted environments. The impedance and compliance control could set impedances of robots so that the...
This paper presents the closed loop teleoperation of a minimal surgery training system using haptic and robot devices. The force tracking performances of system can be improved by using dynamic compensation and fuzzy control. In this system, the master is the 6-DOF haptic device and the slave is the 6-DOF serial robot. The master haptic device provides the trajectories for the slave serial robot throught...
A series elastic actuator (SEA) consists of an actuator in series with a compliant element. By measuring and controlling the displacement of the compliant element, an SEA provides better forward and inverse force control accuracy than traditional stiff actuators. SEAs are suitable for robots that need interact properly with human or environment. Most SEAs use brushless DC motors as the actuators....
Direct force control of robots is challenging, particularly since the interaction with the environment can render the robot unstable. This paper presents the results of novel approaches for passivity-based stability for a particular direct force control method, namely explicit force control. A step-by-step procedure to passivate and stabilise the control loop is presented and it explains how Time...
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...
Autonomous robot hand manipulation has attracted a lot of attention recently. Especially when the robot fingers reach the object, each finger requires the coordination between the position and the force control in free and constrained space. It is not guaranteed to be stable when switching between different control modes. Furthermore, after grasping the object, we also want the system to have the...
Robot manipulation is one of prerequisites capability for service robot. However, autonomous manipulation remains a challenging problem for robot to implement the task, where robot has physical interactions and mechanical contacts with its environment. To date, learning from demonstration (LFD) has been successfully applied to enable robot to acquire new manipulation skill. Researches on LFD mainly...
Body weight support (BWS) is important in rehabilitation robotic systems for patients with locomotion difficulties. We are building an active body weight support (ABWS) system that allows patients to move freely in the three dimensional Cartesian space and provides well-controlled supportive force against gravity. In the BWS unit, both the cable position and tension force on the cable should be controlled...
This paper proposes a data-driven design method of a force controller using input/output data of a force control system, i.e., force response obtained when contacting to an unknown environment and input to a robot at that time. The force control system includes the environment to be contacted in addition to the robot itself. The force controller must be designed in consideration of the environment...
The precise location of tumors is an important step in surgical planning that can be obtained from mechanical properties of soft tissues. In this paper we propose a robotic-assisted palpation system that automatically moves an ultrasound probe to optimize the elastography process and improve the resulting elastogram. The main contribution of this work is the use of the elastography modality directly...
An anti-ejection control strategy was proposed for the characteristics of underactuated prosthetic hand grasping process. The reference position can be calculated and the stiffness of objects can be estimated by the feedback signals of force and position. When the driving joint approaches the reference position and the actual grasp force does not reach the desired value, which means that the ejection...
In force control applications where a robot end-effector is required to interact with the environment or the workpiece, the dynamic of the environment plays an important role. The environment dynamic may influence the performance of the controlled system, especially the performance in transient period. In order to avoid tuning the controller constantly with the changing environment, a robust control...
This paper proposes a force control system including contact process using acceleration-sensor-based instantaneous state observer for high-stiffness gear drive. The proposed system is structured by PI velocity control system and IP force control system based on resonance ratio control system. An instantaneous state observer is used to a resonance ratio control system for a high-stiffness gear drive...
A real snake has simple figure like a string, and has highly adaptability corresponding to the environments/tasks. A snake-like robot mimics such highly adaptability of the real snake, is expected as an adaptable robot corresponding to the environments/tasks. Many literatures have reported with respect to locomotion controls of the snake-like robot, but haven't reported studies for applications. However,...
This paper is based on a prosthetic human organ targeting human arm with simulated / manipulated fingers with a highly related tendon driven mechanism with force sensing feedbacks. The control environment is mostly common to the both real and prosthetic human arms. It is a neural feedback based mechanism which is normally in human arms and here with this project it is integrated with "stall current...
The design of a stable and robust force controller is one of the most important and difficult tasks in rehabilitation robotics. In previous works, the Universal Haptic Pantograph (UHP) was presented as an alternative to conventional arm rehabilitation after a stroke. This robot is composed by a Series Elastic Actuator (SEA) and a Pantograph. In this work an enhanced force control for the UHP is presented...
Power factor in mechanical system is a new concept to express characteristic in mechanical system. It defines dynamic behavior of the impedance characteristic in the motion. However, conventional derivation method requires short-time Fourier transformation in order to consider random input in mechanical system as a combination of sinusoidal waves. This paper proposes a novel method to obtain power...
The ability to refuel satellites on-orbit using teleoperated robots could extend the life of satellite missions, potentially saving time and resources for both industry and space agencies. One critical step in the refueling process is to gain access to the satellite's fueling port by cutting through a seam of tape that adheres two sections of multi-layer insulation (MLI) covering the satellite body...
This paper discusses a new control approach for robotic-assisted tele-echography where contact dynamics are driven by a 3D time-of-flight camera and a force sensor. Based on 3D camera and force data, contact stiffness is anticipated, allowing adaptation before contact. This approach enables to slow down robot dynamics before contact which is adequate for tele-echographic tasks. Additionally, free...
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