371 research outputs found
A review of aerial manipulation of small-scale rotorcraft unmanned robotic systems
Small-scale rotorcraft unmanned robotic systems (SRURSs) are a kind of unmanned rotorcraft with manipulating devices. This review aims to provide an overview on aerial manipulation of SRURSs nowadays and promote relative research in the future. In the past decade, aerial manipulation of SRURSs has attracted the interest of researchers globally. This paper provides a literature review of the last 10 years (2008–2017) on SRURSs, and details achievements and challenges. Firstly, the definition, current state, development, classification, and challenges of SRURSs are introduced. Then, related papers are organized into two topical categories: mechanical structure design, and modeling and control. Following this, research groups involved in SRURS research and their major achievements are summarized and classified in the form of tables. The research groups are introduced in detail from seven parts. Finally, trends and challenges are compiled and presented to serve as a resource for researchers interested in aerial manipulation of SRURSs. The problem, trends, and challenges are described from three aspects. Conclusions of the paper are presented, and the future of SRURSs is discussed to enable further research interests
Performance of modified jatropha oil in combination with hexagonal boron nitride particles as a bio-based lubricant for green machining
This study evaluates the machining performance of newly developed modified jatropha oils (MJO1, MJO3 and MJO5), both with and without hexagonal boron nitride (hBN) particles (ranging between 0.05 and 0.5 wt%) during turning of AISI 1045 using minimum quantity lubrication (MQL). The experimental results indicated that, viscosity improved with the increase in MJOs molar ratio and hBN concentration. Excellent tribological behaviours is found to correlated with a better machining performance were achieved by MJO5a with 0.05 wt%. The MJO5a sample showed the lowest values of cutting force, cutting temperature and surface roughness, with a prolonged tool life and less tool wear, qualifying itself to be a potential alternative to the synthetic ester, with regard to the environmental concern
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)
Adaptive robust interaction control for low-cost robotic grasping
Robotic grasping is a challenging area in the field of robotics. When a gripper starts interacting with an object to perform a grasp, the mechanical properties of the object (stiffness and damping) will play an important role. A gripper which is stable in isolated conditions, can become unstable when coupled to an object. This can lead to the extreme condition where the gripper becomes unstable and generates excessive or insufficient grip force resulting in the grasped object either being crushed, or falling and breaking. In addition to the stability issue, grasp maintenance is one of the most important requirements of any grasp where it guarantees a secure grasp in the presence of any unknown disturbance. The term grasp maintenance refers to the reaction of the controller in the presence of external disturbances, trying to prevent any undesired slippage. To do so, the controller continuously adjusts the grip force. This is a challenging task as it requires an accurate model of the friction and object’s weight to estimate a sufficient grip force to stop the object from slipping while incurring minimum deformation. Unfortunately, in reality, there is no solution which is able to obtain the mechanical properties, frictional coefficient and weight of an object before establishing a mechanical interaction with it. External disturbance forces are also stochastic meaning they are impossible to predict. This thesis addresses both of the problems mentioned above by:Creating a novel variable stiffness gripper, capable of grasping unknown objects, mainly those found in agricultural or food manufacturing companies. In addition to the stabilisation effect of the introduced variable stiffness mechanism, a novel force control algorithm has been designed that passively controls the grip force in variable stiffness grippers. Due to the passive nature of the suggested controller, it completely eliminates the necessity for any force sensor. The combination of both the proposed variable stiffness gripper and the passivity based control provides a unique solution for the stable grasp and force control problem in tendon driven, angular grippers.Introducing a novel active multi input-multi output slip prevention algorithm. The algorithm developed provides a robust control solution to endow direct drive parallel jaw grippers with the capability to stop held objects from slipping while incurring minimum deformation; this can be done without any prior knowledge of the object’s friction and weight. The large number of experiments provided in this thesis demonstrate the robustness of the proposed controller when controlling parallel jaw grippers in order to quickly grip, lift and place a broad range of objects firmly without dropping or crushing them. This is particularly useful for teleoperation and nuclear decommissioning tasks where there is often no accurate information available about the objects to be handled. This can mean that pre-programming of the gripper is required for each different object and for high numbers of objects this is impractical and overly time-consuming. A robust controller, which is able to compensate for any uncertainties regarding the object model and any unknown external disturbances during grasping, is implemented. This work has advanced the state of the art in the following two main areas: Direct impedance modulation for stable grasping in tendon driven, angular grippers. Active MIMO slip prevention grasp control for direct drive parallel jaw grippers
Modeling and control of an anthropomorphic robotic hand
MenciĂłn Europea en el tĂtulo de doctorThis thesis presents methods and tools for enabling the successful use of
robotic hands. For highly dexterous and/or anthropomorphic robotic hands,
these methods have to share some common goals, such as overcoming the
potential complexity of the mechanical design and the ability of performing
accurate tasks with low and efficient computational cost.
A prerequisite for dexterity is to increase the workspace of the robotic hand.
For this purpose, the robotic hand must be considered as a single multibody
system. Solving the inverse kinematics problem of the whole robotic hand is
an arduous task due to the high number of degrees of freedom involved and
the possible mechanical limitations, singularities and other possible constraints.
The redundancy has proven to be of a great usefulness for dealing
with potential constraints. To be able to exploit the redundancy for dealing
with constraints, the adopted method for solving the inverse kinematics
must be robust and extendable. Obviously, addressing such complex problem,
the method will certainly be computationally heavy. Thus, one of the
aims of this thesis is to resolve the inverse kinematics problem of the whole
robotic hand under constraints, taking into account the computational cost.
To this end, this thesis extends and reduces the most recent Selectively
Damped Least Squares method which is based on the computation of all
singular values, to deal with constraints with a minimum computational
cost. New estimation algorithm of singular values and their corresponding
singular vectors is proposed to reduce the computational cost. The reduced
extended selectively damped least squares method is simulated and experimentally
evaluated using an anthropomorphic robotic hand as a test bed.
On the other hand, dexterity depends not only on the accuracy of the position
control, but also on the exerted forces. The tendon driven modern robotic hands, like the one used in this work, are strongly nonlinear dynamic
systems, where motions and forces are transmitted remotely to the
finger joints. The problem of modeling and control of position and force
simultaneously at low level control is then considered. A new hybrid control
structure based on the succession of two sliding mode controllers is
proposed. The force is controlled by its own controller which does not need
a contact model. The performance of the proposed controller is evaluated
by performing the force control directly using the force sensor information
of the fingertip, and indirectly using the torque control of the actuator.
Finally, we expect that the applications of the methods presented in this
thesis can be extended to cover different issues and research fields and in
particular they can be used in a variety of algorithm that require the estimation
of singular values.This work was partially supported by the European project HANDLE, FP7-231640, and by the Spanish ministry MICINN through FPI scholarship within the project DPI-2005-04302.Programa Oficial de Doctorado en IngenierĂa ElĂ©ctrica, ElectrĂłnica y AutomáticaPresidente: Anis Sahbani.- Secretario: Fares Jawad Moh D Abu-Dakka.- Vocal: Claudio Ross
A Review of Pneumatic Actuators Used for the Design of Medical Simulators and Medical Tools
International audienc
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