Gas pressure regulators are widely used in both commercial and residential applications to control the operational pressure of the gas. One common problem in these systems is the tendency for the regulating apparatus to vibrate in an unstable manner during operation. These vibrations tend to cause an auditory hum in the unit, which may cause fatigue damage and failure if left unchecked. This work investigates the stability characteristics of a specific type of hardware and shows the cause of the vibration and possible design modifications that eliminate the unstable vibration modes. A dynamic model of a typical pressure regulator is developed, and a linearized model is then used to investigate the sensitivity of the most important governing parameters. The values of the design parameters are optimized using root locus techniques, and the design trade-offs are discussed.
This paper presents a direct method for haptic rendering of a virtual object in which the object is represented as a virtual kinematic chain (virtual manipulator). The joint angles of the virtual manipulator (VM) are considered as parameters for the object's surface. The present algorithm is based on a closest-point approach that determines the joint angles (surface parameters) uniquely. The joint angles parameterize a point closest to the haptic device end-effector, and an impedance-type controller is designed for the haptic device that accounts for the haptic rendering algorithm. Within the control law, only the forces orthogonal to the object surface are rendered using the Jacobian of the VM, and the user feels a smooth surface whose stability (considering the coupled haptic device dynamics and closest-point algorithm kinematics) is guaranteed. Additional motion constraints on the virtual surface are also created by penalizing the joint angles of the VM, showing how this approach provides an efficient tool in designing a CAD (computer aided design) model. Downloaded from 15 Minsky, M. Computational haptics: the sandpaper H mean curvature system for synthesizing texture for a force-feedback J 2×3 matrix described by any two display. PhD Thesis, Massachusetts Institute of rows of T Technology, Cambridge, Massachusetts, 1995. J e 6×6 Jacobian matrix between ė and ẋ r 16 Hayward, V. and Yi, D. Change of height: an J r 6×6 robot Jacobian matrix approach to the haptic display of shape and texture J v 6×2 VM Jacobian matrix without surface normal. In Experimental robotics J vp , J vs 3×2 Jacobians relating the VM linear VIII, Springer tracts in advanced robotics, 2003, pp. 570-579 (Springer Verlag, Berlin). and angular rates respectively 17 Fisher, W. D. and Mujtaba, M. S. Hybrid position/ J vr 2×3 Jacobian, described between lT
In the approach presented in this research, a six DOF industrial manipulator is used as the master device to provide haptic feedback to the operator. In order develop effective constraints between the motion of the slave and master, a virtual manipulator concept is developed that couples the actual robotic kinematics with the constraints of the simulated slave manipulator. The position and velocity errors between the actual and virtual mechanisms are used to develop an optimal impedance controller that constrains the motion of the master in all directions that are orthogonal to the allowable motions of the slave. This approach allows the use of a conventional industrial manipulator as an effective haptic display device.
This work presents a commentary of the article published by Asl and Ulsoy (2003, ASME J. Dyn. Syst., Meas., Control, 125, pp. 215–223). We show by an example that their method leads to inaccurate results and is therefore erroneous.
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