Showing 4 results for Haptic
Vahid Aberoomand, Rasul Fesharakifard, Ali Kamal Eigoli,
Volume 16, Issue 12 (2-2017)
Abstract
In electromagnetic motors, increase in output torque leads to increase in rotor inertia. Various robotics applications, especially haptic interfaces, oblige convenient dynamic performances of electromagnetic motors which are strongly in turn influenced by the rotor’s inertia. In the present paper, a robust control method for a viscous hybrid actuator is developed which supplies a desired varying torque while maintaining a constant low inertia. This hybrid actuator includes two dc motors with the shafts coupled through a rotational damper using a viscous non-contact coupler. This coupling method is based on Eddy current to provide the required performances. The large far motor eliminates or reduces the inertial forces and external dynamics effects on the actuator. The small near motor provides the desired output torque. Since the system is essentially linear, the applied robust control method is based on Hꝏ and parametric uncertainties and physical constraints including motors’ voltages saturation, rotary damper’s speed saturation, fastest user’s speed and acceleration applied to the actuator and force sensor noise are considered in its design. Also the robust method of µ-synthesis for the system in presence of parameteric uncertainties and other physical constraints are studied. The implementation of the controller on a 1 dof haptic interface model validate the achievement of the desired performances.
Alireza Hadi, Mohammad Ali Bagherian Jafarabadi,
Volume 17, Issue 5 (7-2017)
Abstract
Individuals with high levels of disability like patients with cervical spinal cord injury, are highly dependant on their relatives for daily life needs. Hence, this problem decreases the quality of life of this individuals and their relatives. New technologies such as robotics have the potential to help these kind of patients and give them some degree of independence. The first step in design and implementation of robots which have the capability of helping disabled people is to design a user interface that can receive user’s commands and transfer these commands into the robot environment. In this paper, a haptic user interface has been designed and implemented to serve patients with cervical spinal cord injury. In this user interface, user’s head angles have been extracted using a gyroscope sensor and then transferred into the computer simulation environment in which the robotic arm is graphically simulated and the user can control the arm using his/her head movements through a novel control pattern. A haptic unit has also designed and implemented to produce resistive torques against head movements to help user to physically sense the weight of gripped objects and the collision of the robotic arm with obstacles. The performance of haptic user interface evaluated using three sets of tests subject to two healthy individuals. Finally, obstacle collision detection tests was 100 percent successfully while heavy and light object recognition tests were 83 percent and heavy, medium and light object recognition tests were 72 percent successful.
Ahmad Mashayekhi, Saeed Behbahani, Fanny Ficuciello, Bruno Siciliano,
Volume 17, Issue 10 (1-2018)
Abstract
One of the main challenges of simulating virtual objects by haptic devices is instability, especially in simulating stiff objects. In this paper, a stability criterion for a haptic device is derived using Lyapunov approach. The haptic device is modeled as a mass and viscous friction, which has to simulate the touching a virtual environment (VE) with specified stiffness and damping. Dynamic equations and state-space equations are derived with assumption of small values of sampling time, time delay and virtual damping. A Lyapunov function is proposed, consisting of summation of kinetic and potential energy of the system, plus two unknown terms. Each one of these two unknown terms is a function of one system states (i.e. position and velocity). These two functions are determined so that, from one side the Lyapunov function be positive definite, and from the other side the stability criterion is reached with putting time derivation of the Lyapunov function negative. The stability condition determined by this method is a linear criterion between maximum permissible virtual stiffness, virtual damping of the VE, physical damping of the haptic device, sampling time and time delay, and is consistent with the results of previous researches with linear methods. The importance of the presented analysis in this paper is that this method can be extended by adding new terms to the Lyapunov function, to remove some limitations and to take into account nonlinear effects. Presented criterion and its results are verified by experiments on KUKA robot.
A. Gholami, M. Majidi, S. Raeisdana, V. Tavoosi,
Volume 20, Issue 2 (1-2020)
Abstract
The torque feedback of the vehicle's steering wheel or driver perception of the steering wheel is one of the aspects of steering quality that has been investigated extensively in recent decades. In this paper, the driver model for sensing torque feedback or haptic interaction between the vehicle equipped with a steer-by-wire system (SWB) and the driver has been designed. The driver model consists of a preview model and a neuromuscular model. The preview driver model calculates the desired angle of the steering wheel to follow the path, and the neuromuscular driver model that can perceive real-time torque feedback determines the real angle of the steering wheel according to muscular system transfer functions to follow its desired angle. Calculating of torques on the steering wheel requires estimation of the tire-road forces. Whereas directly calculating the tire-road forces is too difficult, particularly in the lateral vehicle dynamics, suitable estimator to estimate these forces designed. The simulation results using the Carsim and Simulink software indicate that the driver model performance improved 63 % when torque feedback is enabled. So the designed driver model with torque feedback has an important role in controlling and vehicle steering in conducting double lane-change maneuvers.