No abstract

A compliant constant-force mechanism is a passive force regulation device that can generate a nearly constant output force over a range of input or output displacements while without the use of sensors and feedback control. In topology synthesis of a compliant constantforce mechanism for a given input displacement range, the constant output force can be achieved by maintaining the output displacement to be nearly a same value while the input displacement increases. In order to further control the desired output displacement for the compliant constantforce mechanism before contacting the object, this article introduces a new composite objective function that can consider both the output force (with contact) and the output displacement (without contact) of the synthesized compliant mechanism. The sensitivity for the proposed objective function with respect to the element density is derived while considering the effect of nonlinearity in the large deformation condition. The proposed topology optimization method is used to design an innovative constant-force compliant finger, and its prototype is manufactured by 3-D printing using a flexible thermoplastic elastomer. The experimental results show the developed constant-force compliant finger can provide a nearly constant output force of 41.9 N over the input displacement ranging from 15 to 30 mm while the maximum and average force variations within the constant-force range are 2.2% and 0.9%, respectively. In addition, the developed constant-force compliant finger is used to design a three-fingered constant-force compliant gripper that can be used in robotic grasping of fragile objects.

No abstract

Abstract-This paper investigates the control and safety of a series of maglev trains moving on multi-span simply supported bridges with the foundation settlements. To control the dynamic response of the maglev trains, a PI (proportional-integral) controller with constant tuning gains is applied. The finite element results indicate that the influences of the rail irregularities are obvious. However, the allowable vertical settlement and the Y-deflection of the bridge, which is caused by the X-rotation can be significantly improved when the lateral electromagnetic force is enlarged.

This paper proposed an efficient method based on theoretical equations to solve the dynamic interaction problem between the Timoshenko beam and maglev vehicles. A systematic PI numerical scheme is developed for the control system of the maglev train. The major advantage is that only one simple equation required in the control calculation, although the original control system is fairly complicated. Numerical simulations indicate that a large time step length can be used in the proposed method to obtain stable and accurate results.