226 research outputs found
Active compliance control strategies for multifingered robot hand
Safety issues have to be enhanced when the robot hand is grasping objects of
different shapes, sizes and stiffness. The inability to control the grasping force and
finger stiffness can lead to unsafe grasping environment. Although many researches
have been conducted to resolve the grasping issues, particularly for the object with
different shape, size and stiffness, the grasping control still requires further
improvement. Hence, the primary aim of this work is to assess and improve the safety
of the robot hand. One of the methods that allows a safe grasping is by employing an
active compliance control via the force and impedance control. The implementation of
force control considers the proportional–integral–derivative (PID) controller.
Meanwhile, the implementation of impedance control employs the integral slidingmode
controller (ISMC) and adaptive controller. A series of experiments and
simulations is used to demonstrate the fundamental principles of robot grasping.
Objects with different shape, size and stiffness are tested using a 3-Finger Adaptive
Robot Gripper. The work introduces the Modbus remote terminal unit [RTU] protocol,
a low-cost force sensor and the Arduino IO Package for a real-time hardware setup. It
is found that, the results of the force control via PID controller are feasible to maintain
the grasped object at certain positions, depending on the desired grasping force (i.e.,
1N and 8N). Meanwhile, the implementation of impedance control via ISMC and
adaptive controller yields multiple stiffness levels for the robot fingers and able to
reduce collision between the fingers and the object. However, it was found that the
adaptive controller produces better impedance control results as compared to the
ISMC, with a 33% efficiency improvement. This work lays important foundations for
long-term related research, particularly in the field of active compliance control that
can be beneficial to human–robot interaction (HRI)
Modelling and Interactional Control of a Multi-fingered Robotic Hand for Grasping and Manipulation.
PhDIn this thesis, the synthesis of a grasping and manipulation controller of the Barrett hand, which
is an archetypal example of a multi-fingered robotic hand, is investigated in some detail. This
synthesis involves not only the dynamic modelling of the robotic hand but also the control
of the joint and workspace dynamics as well as the interaction of the hand with object it is
grasping and the environment it is operating in. Grasping and manipulation of an object by a
robotic hand is always challenging due to the uncertainties, associated with non-linearities of
the robot dynamics, unknown location and stiffness parameters of the objects which are not
structured in any sense and unknown contact mechanics during the interaction of the hand’s
fingers and the object. To address these challenges, the fundamental task is to establish the
mathematical model of the robot hand, model the body dynamics of the object and establish
the contact mechanics between the hand and the object.
A Lagrangian based mathematical model of the Barrett hand is developed for controller implementation.
A physical SimMechanics based model of the Barrett hand is also developed in
MATLAB/Simulink environment. A computed torque controller and an adaptive sliding model
controller are designed for the hand and their performance is assessed both in the joint space
and in the workspace. Stability analysis of the controllers are carried out before developing the
control laws. The higher order sliding model controllers are developed for the position control
assuming that the uncertainties are in place. Also, this controllers enhance the performance by
reducing chattering of the control torques applied to the robot hand.
A contact model is developed for the Barrett hand as its fingers grasp the object in the operating
environment. The contact forces during the simulation of the interaction of the fingers with
the object were monitored, for objects with different stiffness values. Position and force based
impedance controllers are developed to optimise the contact force. To deal with the unknown
stiffness of the environment, adaptation is implemented by identifying the impedance. An evolutionary
algorithm is also used to estimate the desired impedance parameters of the dynamics
of the coupled robot and compliant object.
A Newton-Euler based model is developed for the rigid object body. A grasp map and a hand
Jacobian are defined for the Barrett hand grasping an object. A fixed contact model with
friction is considered for the grasping and the manipulation control. The compliant dynamics of Barrett hand and object is developed and the control problem is defined in terms of the
contact force. An adaptive control framework is developed and implemented for different
grasps and manipulation trajectories of the Barrett hand. The adaptive controller is developed
in two stages: first, the unknown robot and object dynamics are estimated and second, the
contact force is computed from the estimated dynamics. The stability of the controllers is
ensured by applying Lyapunov’s direct method
Sensors for Robotic Hands: A Survey of State of the Art
Recent decades have seen significant progress in the field of artificial hands. Most of the
surveys, which try to capture the latest developments in this field, focused on actuation and control systems of these devices. In this paper, our goal is to provide a comprehensive survey of the sensors for artificial hands. In order to present the evolution of the field, we cover five year periods starting at the turn of the millennium. At each period, we present the robot hands with a focus on their sensor systems dividing them into categories, such as prosthetics, research devices, and industrial end-effectors.We also cover the sensors developed for robot hand usage in each era. Finally, the period between 2010 and 2015 introduces the reader to the state of the art and also hints to the future directions in the sensor development for artificial hands
Aerial Manipulation: A Literature Review
Aerial manipulation aims at combining the versatil- ity and the agility of some aerial platforms with the manipulation capabilities of robotic arms. This letter tries to collect the results reached by the research community so far within the field of aerial manipulation, especially from the technological and control point of view. A brief literature review of general aerial robotics and space manipulation is carried out as well
Development of a Novel Impedance-Controlled Quasi-Direct-Drive Robot Hand
Most robotic hands and grippers rely on actuators with large gearboxes and
force sensors for controlling gripping force. However, this might not be ideal
for tasks which require the robot to interact with an unstructured and/or
unknown environment. We propose a novel quasi-direct-drive two-fingered robotic
hand with variable impedance control in the joint space and Cartesian space.
The hand has a total of four degrees of freedom, a backdrivable gear train, and
four brushless direct current (BLDC) motors. Field-Oriented Control (FOC) with
current sensing is used to control motor torques. Variable impedance control
allows the hand to perform dexterous manipulation tasks while being safe during
human-robot interaction. The quasi-direct-drive actuators enable the fingers to
handle contact with the environment without the need for complicated tactile or
force sensors. A majority 3D printed assembly makes this a low-cost research
platform built with affordable off-the-shelf components. The hand demonstrates
grasping with force-closure and form-closure, stable grasps in response to
disturbances, tasks exploiting contact with the environment, simple in-hand
manipulation, and a light touch for handling fragile objects.Comment: 75 pages, A Thesis in Partial Fulfillment of the Requirements for the
Degree of Master of Science in Mechanical Engineering at Stony Brook
Universit
Variable stiffness robotic hand for stable grasp and flexible handling
Robotic grasping is a challenging area in the field of robotics. When interacting with an object, the dynamic properties of the object will play an important role where a gripper (as a system), which has been shown to be stable as per appropriate stability criteria, can become unstable when coupled to an object. However, including a sufficiently compliant element within the actuation system of the robotic hand can increase the stability of the grasp in the presence of uncertainties. This paper deals with an innovative robotic variable stiffness hand design, VSH1, for industrial applications. The main objective of this work is to realise an affordable, as well as durable, adaptable, and compliant gripper for industrial environments with a larger interval of stiffness variability than similar existing systems. The driving system for the proposed hand consists of two servo motors and one linear spring arranged in a relatively simple fashion. Having just a single spring in the actuation system helps us to achieve a very small hysteresis band and represents a means by which to rapidly control the stiffness. We prove, both mathematically and experimentally, that the proposed model is characterised by a broad range of stiffness. To control the grasp, a first-order sliding mode controller (SMC) is designed and presented. The experimental results provided will show how, despite the relatively simple implementation of our first prototype, the hand performs extremely well in terms of both stiffness variability and force controllability
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