Modeling And Stability Issues In Force Feedback System Based On Virtual Reality

As a new human-computer interaction technology, Force feedback technology enables operator to feel and manipulate the simulated objects. Combined with visual rendering, haptic rendering leads to a more realistic of virtual reality system, it has been more widely used In the medical, military and other fields. This article discusses the force feedback system which based on Virtual environment by evaluating the haptic system stability.Firstly, for discussion of different virtual environments and force feedback device parameters on the performance of the system, according to the mathematical model of force feedback devices and different attributes of virtual environment, it set up the open loop system without operator, and according to Routh-Hurwitz stable criterion, it has given the necessary conditions to maintain system stability and MATLAB is used as simulation implementation.Secondly, A detailed energy compensating method is presented based on the concept of doing work, using ideal continuous-time haptic system as a reference, and"energy-compensating controller"is defined which compensates for force feedback system in the energy flow differences between each sampling period, this method not only removes the unwanted extra energy from the VE but also compensates for the deficient energy that should flow into the VE. Through compared experiments that based on the virtual wall system, it shows that the method can effectively improve system stability and authenticity of simulation.Finally, for the problem that the accurate impedance of deformable objects is rare and the stability of the force feedback system under stiffness of the environment, based on passivity theory and the two-port network model, it presents a control method using an adjusting output-limiter. This method can guarantee the passivity of the haptic system through adjusting the maximum permissible force. The controller only concerned with size of the mapping force and don't need considerate the force model, therefore it adapted to the various virtual environments. The controller is also adapted to the impedance and admittance-type force-based feedback system, it also can be applied to many degrees of freedom interaction. Finally, the experiment under the environment of the large stiffness is setup and the results indicate that the proposed method can effectively eliminate vibration and stable interaction can be realized.