The Development of a Direct Drive Master Arm

1990 ◽  
Vol 2 (6) ◽  
pp. 463-470 ◽  
Author(s):  
Tetsuo Kotoku ◽  
◽  
Erhard J. Hüsler ◽  
Kazuo Tanie ◽  
Akio Fujikawa
Keyword(s):  
High Resolution ◽  
Impedance Control ◽  
Angular Displacement ◽  
Angular Acceleration ◽  
Mechanical Impedance ◽  
Control Law ◽  
Direct Drive ◽  
Constraint Forces ◽  
Displacement Sensors ◽  
Arm Motion

This paper deals with the development of a 4 degree of freedom direct drive master manipulator system which has the ability of virtually adjusting its mechanical impedance. In the field of bilateral master-slave manipulation, there are some important points to be considered when a master manipulator is designed. One point is related to how to measure the human operator’s arm motion with high accuracy (which the operator produces to teach the trajectory of tasks). Another point is how to design an effective force/torque generator to make an operator feel the constraint forces the slave arm will receive from the environments during tasks. To satisfy these requirements, a manipulator with a variable mechanical impedance structure and joints equipped with high resolution angular displacement sensors is expected to be developed. The use of the variable impedance structure provides a capability of reflecting the constraint forces to an operator not only statically, but also dynamically. This is effective to present the constraints to an operator with high fidelity. In the research, joint mechanisms and joint sensors suitable for the impedance control were discussed, while the mechanical structure of the master manipulator which is effective to construct a simple impedance control law was investigated. With these considerations in mind, a master manipulator was designed and its impedance control law was formulated. The features of the manufactured manipulator are summarized as follows; (1) each joint is driven by a direct drive torque motor with less friction and has a high resolution angular encoder attached to a processor which can provide joint angular displacement, angular velocity and angular acceleration. (2) the manipulator has the decoupled and configuration-invariant inertia structure in part which is effective to simplify impedance control law. In the paper, the design concept of the master manipulator is first discussed. Secondly, the details of the manufactured manipulator structure are explained. Finally, the results of the evaluation experiments are described and the fundamental characteristics of the system are confirmed.

Functional Recovery of the Upper Limb With an Active Personal Device

2014 ◽  
Author(s):  
Federico Casolo ◽  
Gianluca Savalli
Keyword(s):  
Upper Limb ◽  
Functional Recovery ◽  
Impedance Control ◽  
Mechanical Impedance ◽  
Patient Characteristics ◽  
Memory Space ◽  
Working Volume ◽  
Intention To Move ◽  
The Subject ◽  
Arm Motion

A new personal device to assist the upper limb capable to be mounted on a wheelchair is being tested. The robot is equipped with three brushless motors powered by four electronic boards appositely designed and communicating via I2C protocol; one board works as master for the other three, which have simpler tasks. Most of the driving software has been developed with Matlab and mainly translated into C++ for memory space and boards’ efficiency matters. The system’s end-effector is connected to the subject’s forearm and can cooperate to the arm motion in several different ways. In order to avoid the overstress of the natural joints no further connections are made to the upper limb. The working volume of the limb connected to the device allows the execution of the trajectories required for most of daily living activities. It is addressed to post stroke rehabilitation and to the self-treatment of other patients with serious deficiency of arm forces, like individuals affected by muscular dystrophy. Some working modes exploit the mechanical impedance control to gently interfere with the residual natural motion capability of the subjects. The very preliminary tests of the prototype fitted on a power wheelchair are encouraging: it is light, not too noisy and easy to move for the subject. The first working mode, with full arm gravity compensation, and the second working mode, with partial compensation, have been implemented and are currently being tested with patients, as well as the mode in which the subject is helped to repeat a stereotyped exercise for self-physiotherapy. Beside the fact the control system must be calibrated on patient characteristics, for these initial tasks the system reveals to be user-friendly. Other working modes require to interpret the patient intention to move the upper limb. For a natural approach it is sufficient to decode the movement intention of the patient and the final position he wants the hand to reach, whilst the rest of the limb can be automatically positioned by the system. Different approaches to solve the problem have been experimentally tested, including the use of a headgear with a brain interface. To present knowledge the best results have been obtained by monitoring the movement of another body segment such as the head. The device designed for the functional recovery of upper limb can furthermore be used to monitor and easily certify the evolution of the patient conditions.

SKELETAL MUSCLE IMPEDANCE IN THE CONTROL OF MOTOR ACTIONS

2002 ◽  
Vol 02 (03n04) ◽  
pp. 359-373 ◽  
Author(s):  
NEVILLE HOGAN
Keyword(s):  
Skeletal Muscle ◽  
Impedance Control ◽  
Mechanical Impedance ◽  
Physical Interaction ◽  
Constraint Forces ◽  
Contact Stability ◽  
Antagonist Muscles ◽  
Force Components ◽  
Motor Actions ◽  
Task Goals

Unlike ideal engineering actuators, skeletal muscle has neither zero nor infinite mechanical impedance. Non-zero neuro-motor mechanical impedance is required to stabilize posture; its possible contribution to movement will briefly be considered. The essential role of variable mechanical impedance to control physical interaction with objects will be described. Evidence that humans voluntarily control impedance to achieve task goals will be reviewed. Robot impedance control is a biologically-inspired approach to controlling robot interaction. How robust contact stability may be achieved by constraining mechanical impedance will be detailed. One robot application requiring contact and cooperation between robots and humans is robotic physiotherapy. Experience to date demonstrating the success of robotic neuro-rehabilitation of patients recovering from stroke will be summarized. Analysis of the geometry of musculo-skeletal attachment reveals that force control may require synergistic co-contraction of apparently antagonist muscles, rendering the conventional anatomical definition of synergist and antagonist muscles ambiguous. Analysis of workless constraint forces show that they may be used to economize muscle effort; exerting force components normal to a kinematic constraint never requires more muscle effort than exerting purely tangential forces.

scholarly journals Manipulator Trajectory Tracking with a Neural Network Adaptive Control Method

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Wenbin Zha ◽  
Hui Zhang ◽  
Xiangrong Xu
Keyword(s):  
Neural Network ◽  
Adaptive Control ◽  
Control Method ◽  
Angular Displacement ◽  
Angular Acceleration ◽  
Control Law ◽  
Time Varying ◽  
Dynamics Model ◽  
The Neural Network ◽  
Input Torque

In order to solve the joint chattering problem of the manipulator in the process of motion, a novel dynamics model is established based on the dynamics model of the manipulator, by fitting parameters of the neural network and combining with the estimated value of the inertia matrix. We proposed a neural network adaptive control method with a time-varying constraint state based on the dynamics model of estimation. We design the control law, establish the Lyapunov function equation and the asymmetric term, and derive the convergence of the control law. According to the joint state tracking results of the manipulator, the angular displacement, angular velocity, angular acceleration, input torque, and disturbance fitting of the manipulator are analyzed by using the Simulink and Gazebo. The simulation results show that the proposed method can effectively suppress the chattering amplitude under the environment disturbances.

Dynamic Model Development of Wind Turbine Drivetrains by Using Sensor Measurements

2021 ◽  
Author(s):  
Diederik van Binsbergen ◽  
Amir R. Nejad ◽  
Jan Helsen
Keyword(s):  
Wind Turbine ◽  
Angular Displacement ◽  
Model Development ◽  
Rotational Frequency ◽  
Sensor Data ◽  
Gear Mesh ◽  
Modal Properties ◽  
Vibration Sensors ◽  
Displacement Sensors ◽  
Simulation Based

Abstract This paper aims to analyze the feasibility of establishing a dynamic drivetrain model from condition monitoring measurements. In this study SCADA data and further sensor data is analyzed from a 1.5MW wind turbine, provided by the National Renewable Energy Laboratory. A multibody model of the drivetrain is made and simulation based sensors are placed on bearings to look at the possibility to obtain geometrical and modal properties from simulation based vibration sensors. Results show that the axial proxy sensor did not provide any usable system information due to its application purpose. SCADA data did not meet the Nyquist frequency and cannot be used to determine geometrical or modal properties. Strain gauges on the shaft can provide the shaft rotational frequency, while torque and angular displacement sensors can provide the torsional eigenfrequency of the system. Simulation based vibration sensors are able to capture gear mesh frequencies, harmonics, sideband frequencies and shaft rotational frequencies.

On the Spatial Compliance of Robotic Manipulators

1997 ◽  
Vol 119 (4) ◽  
pp. 839-844 ◽  
Author(s):  
E. D. Fasse
Keyword(s):  
Spatial Reasoning ◽  
Impedance Control ◽  
Control Law ◽  
Spatial Transformation ◽  
Compliance Control ◽  
Interactive Control ◽  
Control Schemes ◽  
Stiffness Control ◽  
Geometrical Version ◽  
Spatial Compliance

Interactive control schemes, such as stiffness control and impedance control, are widely accepted as a means to actively accommodate environmental forces, but have not been widely applied. This is in part because well-known controllers are parametrized in a mathematically convenient, but nonintuitive way. “Spatial compliance control” is a Euclidean-geometrical version of compliance control that is parametrized in an intuitive way. A family of compliances is introduced with spatial transformation properties that simplify spatial reasoning aspects of compliance parameter selection. A control law is derived assuming that the robot consists of a serial linkage of rigid links actuated by variable-effort actuators.

A Sliding Mode Observer-Based Icing Detection and Estimation Scheme for Wind Turbines

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Maria Letizia Corradini ◽  
Gianluca Ippoliti ◽  
Giuseppe Orlando
Keyword(s):  
Renewable Energy ◽  
Wind Turbines ◽  
Sliding Mode ◽  
Angular Acceleration ◽  
Power Coefficient ◽  
Control Law ◽  
National Renewable Energy Laboratory ◽  
Robust Observer ◽  
Medium Speed ◽  
Estimation Scheme

In this paper, the problem of icing detection is considered for wind turbines (WTs) operating in medium speed wind region (region 2) and subject to a control law tracking the maximum delivery point of the power coefficient characteristic. Based on a robust observer of the rotor angular acceleration, rotor inertia is estimated in order to detect its eventual increase due to icing. Moreover, the observed value of rotor inertia can be potentially used for updating the controller parameters or to stop the turbine when icing is too severe. The proposed approach has been tested by intensive MatLab® simulations using the National Renewable Energy Laboratory 5 MW WT model.

Estimation of Interstitial Velocity Using a Direct Drive High‐Resolution Passive Profiler

Ground Water ◽  
2019 ◽  
Vol 57 (6) ◽  
pp. 915-924
Author(s):  
Haley A. Schneider ◽  
W. Andrew Jackson ◽  
Ken Rainwater ◽  
Danny Reible ◽  
Stephen Morse ◽  
...  
Keyword(s):  
High Resolution ◽  
Direct Drive ◽  
Interstitial Velocity
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