141 research outputs found
Control Software of Robot Compliant Wrist System
The compliant wrist combining passive compliants and sensor has been developed in GRASP laboratory. The device provides the robot system the necessary flexibility which accommodates transitions as the robot makes contact with the environment, corrects positioning error in automatic assembly, avoids high impact forces and protects the surface from damage. The device also supplies the displacement sensing of the passive compliance so that active feedback control is possible.
This report is intended to serve as a reference material to introduce the control software of the robot compliant wrist system developed and implemented in the lab. The detail discussion on system performance and parameters selection can be found in the thesis [3].
The rest of material is organized as follows.
Section 2 introduces the compliance control methods of robot manipulators. The historic development of both passive and active compliance method is discussed. The advantages and disadvantages of the methods are investigated. Based on the unsolved problems in this issue, the six-degree freedom compliant wrist is developed, and the design feature is presented.
Section 3 discusses the hybrid position/force control scheme using the sensing information from the device. The positioning error due to load or external force when robot moves in free space is compensated for, so that the effective stiffness is increased. In force control when robot is constrained by environment, the trajectory is modified by sensed force, so that the effective stiffness is decreased.
Section 4 deals with the implementation of the control scheme. Various programs have been developed to perform the hybrid control operations, such as hybrid control demonstration, surface tracking, edge tracking, insertion and pulling out, and writing operation. The programs have been successfully implemented in the experiments. Definition and selection of the parameters in the programs are discussed.
Section 5. is the source code of control scheme which has been implemented in PUMA 560 with index machine in GRASP Laboratory. The control is executed on a MicroVax I1 using the RCI primitives of RCCL
Gyroscopically Stabilized Robot: Balance and Tracking
The single wheel, gyroscopically stabilized robot - Gyrover, is a dynamically
stable but statically unstable, underactuated system. In this paper, based on
the dynamic model of the robot, we investigate two classes of nonholonomic
constraints associated with the system. Then, based on the backstepping
technology, we propose a control law for balance control of Gyrover. Next,
through transferring the systems states from Cartesian coordinate to polar
coordinate, control laws for point-to-point control and line tracking in
Cartesian space are provided
Dynamic Balance Control of Multi-arm Free-Floating Space Robots
This paper investigates the problem of the dynamic balance control of
multi-arm free-floating space robot during capturing an active object in close
proximity. The position and orientation of space base will be affected during
the operation of space manipulator because of the dynamics coupling between the
manipulator and space base. This dynamics coupling is unique characteristics of
space robot system. Such a disturbance will produce a serious impact between
the manipulator hand and the object. To ensure reliable and precise operation,
we propose to develop a space robot system consisting of two arms, with one arm
(mission arm) for accomplishing the capture mission, and the other one (balance
arm) compensating for the disturbance of the base. We present the coordinated
control concept for balance of the attitude of the base using the balance arm.
The mission arm can move along the given trajectory to approach and capture the
target with no considering the disturbance from the coupling of the base. We
establish a relationship between the motion of two arm that can realize the
zeros reaction to the base. The simulation studies verified the validity and
efficiency of the proposed control method
Robotic Exploration of Surfaces With a Compliant Wrist Sensor
This paper presents some results of an ongoing research project to investigate the components and modules that are necessary to equip a robot with exploratory capabilities. Of particular interest is the recovery of certain material properties from a surface, given minimal a priori information, with the intent to use this information to enable a robot to stand and walk stably on a surface that is unknown and unconstrained. To this end, exploratory procedures (ep\u27s) have been designed and implemented to recover penetrability, material hardness and surface roughness by exploring the surface using a compliant wrist sensor. A six degree-of-freedom compliant wrist sensor, which combines passive compliance and active sensing, has been developed to provide the necessary flexibility for force and contact control, as well as to provide accurate position control. This paper describes the compliant wrist and sensing mechanism design along with a hybrid control algorithm that utilizes the sensed information from the wrist to adjust the apparent stiffness of the end-effector as desired
Support Vector Machine for Behavior-Based Driver Identification System
We present an intelligent driver
identification system to handle vehicle theft based on modeling
dynamic human behaviors. We propose to recognize illegitimate
drivers through their driving behaviors. Since human driving
behaviors belong to a dynamic biometrical feature which is
complex and difficult to imitate compared with static features
such as passwords and fingerprints, we find that this novel
idea of utilizing human dynamic features for enhanced security
application is more effective. In this paper, we first describe
our experimental platform for collecting and modeling human
driving behaviors. Then we compare fast Fourier transform
(FFT), principal component analysis (PCA), and independent
component analysis (ICA) for data preprocessing. Using machine
learning method of support vector machine (SVM), we derive the individual
driving behavior model and we then demonstrate
the procedure for recognizing different drivers by analyzing
the corresponding models. The experimental results of learning
algorithms and evaluation are described
Towards Better Accuracy-efficiency Trade-offs: Divide and Co-training
The width of a neural network matters since increasing the width will
necessarily increase the model capacity. However, the performance of a network
does not improve linearly with the width and soon gets saturated. In this case,
we argue that increasing the number of networks (ensemble) can achieve better
accuracy-efficiency trade-offs than purely increasing the width. To prove it,
one large network is divided into several small ones regarding its parameters
and regularization components. Each of these small networks has a fraction of
the original one's parameters. We then train these small networks together and
make them see various views of the same data to increase their diversity.
During this co-training process, networks can also learn from each other. As a
result, small networks can achieve better ensemble performance than the large
one with few or no extra parameters or FLOPs. Small networks can also achieve
faster inference speed than the large one by concurrent running on different
devices. We validate our argument with 8 different neural architectures on
common benchmarks through extensive experiments. The code is available at
\url{https://github.com/mzhaoshuai/Divide-and-Co-training}
A Distributed System for Robot Manipulator Control, NSF Grant ECS-11879 Fourth Report
This is the fourth annual report representing our last year\u27s work under the current grant. This work was directed to the development of a distributed computer architecture to function as a force and motion server to a robot system. In the course of this work we developed a compliant contact sensor to provide for transitions between position and force control; developed an end-effector capable of securing a stable grasp on an object and a theory of grasping; developed and built a controller which minimizes control delays; explored a parallel kinematics algorithms for the controller; developed a consistent approach to the definition of motion both in joint coordinates and in Cartesian coordinates; developed a symbolic simplification software package to generate the dynamics equations of a manipulator such that the calculations may be split between background and foreground
A Distributed System for Robot Manipulator Control
This is the final report representing three years of work under the current grant. This work was directed to the development of a distributed computer architecture to function as a force and motion server to a robot system. In the course of this work we developed a compliant contact sensor to provide for transitions between position and force control; we have developed an end-effector capable of securing a stable grasp on an object and a theory of grasping; we have built a controller which minimizes control delays, and are currently achieving delays of the order of five milliseconds, with sample rates of 200 hertz; we have developed parallel kinematics algorithms for the controller; we have developed a consistent approach to the definition of motion both in joint coordinates and in Cartesian coordinates; we have developed a symbolic simplification software package to generate the dynamics equations of a manipulator such that the calculations may be split between background and foreground
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