Due to their monolithic construction and superior wear and loss properties, flexure joints have been used to reduce the mechanism size and increase the positioning accuracy. The compliance of flexure joints, however, can affect the static and dynamic characteristics of the overall mechanism. To design mechanisms containing flexure joints, we have proposed a multi-objective optimization approach to take into account the multitude of performance metrics and design constraints. A Pareto frontier is first computed, and secondary design criteria, such as sensitivity and dynamic characteristics, are then applied to select the final design. To reduce the computation load and facilitate design iteration, a lumped spring approximation, the Paros-Weisbord model, is used to characterize the flexure joints and the pseudo-rigid-body model is used as an approximate description of mechanisms. This paper presents this approach applied to the design of a micro-gripper. The performance metrics are chosen to be the manipulability of the gripper opening and the decoupling of a stiffness matrix (reflecting the remote center of compliance criterion). Different design and initial fabrication results are included

Flexure joints are frequently used in precision-motion stages and microrobotic mechanisms due to their monolithic construction. The joint compliance, however, can affect the static and dynamic performance of the overall mechanism. In this paper, we consider the analysis and design of general platform-type parallel mechanisms containing flexure joints. Based on static performance measures such as task-space stiffness and manipulability, and constraints such as joint stress, mechanism size, and workspace volume, we pose the design problem as a multiobjective optimization. We first calculate the Pareto frontier, which can then be used to select the desired design parameters based on secondary criteria, such as performance sensitivity and dynamic characteristics. To facilitate design iteration, we apply the pseudo rigid-body approach with a lumped approximation of the flexure joints. A planar mechanism is used to illustrate the analysis and design techniques.

Flexure joints are frequently used in precision motion stages and micro-robotic mechanisms due to their monolithic construction. The joint compliance, however, can affect the static and dynamic performance of the overall mechanism. In this paper, we consider the analysis and design of general platform type parallel mechanisms containing flexure joints. We consider static performance measures such as task space stiffness and manipulability, while subject to constraints such as joint stress, mechanism size, workspace volume, and dynamic characteristics. Based on these performance measures and constraints, we adopt the multi-objective optimization approach. We first obtain the Pareto frontier, which can then be used to select the desired design parameters based on secondary criteria such as performance sensitivity. To simplify presentation, we consider only lumped approximation of flexure joints in the pseudo-rigid-body approach. A planar mechanism is included to illustrate the analysis and design techniques. Tools presented in this paper can also be applied to a broader class of compliant mechanisms, including robots with inherent joint flexibility as well as compliant robots for contact tasks.

This paper presents analytical, simulation and experimental results from a study of compliant insertion tasks in microassembly. Gripper compliance is desirable to compensate for positional errors and to prevent the breakage of a gripper during assembly tasks. An analytical model is derived to study the motion and force profiles during compliant insertion. Thermal bimorph microgrippers with a compliant tip are designed and fabricated using a silicon DRIE process, and are mounted on a precision motion stage. A series of micropeg manipulation tasks such as pick up, rotation, and insertion are successfully performed. Finally, a comb structure is integrated in the gripper to calculate insertion force by measuring the deflection of a gripper, which is essential for automated microassembly.

Thermal bimorphs are a popular actuation technology in MEMS (micro-electro-mechanical systems). Their operating principle is based on differential thermal expansion induced by Joule heating. Thermal bimorphs, and other thermal flexure actuators have been used in many applications, from micro-grippers, to micro-optical mirrors. In most cases open-loop control is used to difficulties in fabricating positioning sensors together with actuator. In this paper we present several methods for extracting reduced-order thermal flexure actuator models based on experimental data, physical principles, and FEA simulation. We then use the models to generate optimal driving signals using input shaping techniques. Both simulation and experimental results are included to illustrate the efficacy of our approach. This framework can also be applied to other types of MEMS actuators, including electrostatic comb drives.

The assembly of parts with dimensions several hundred microns or less is a challenging problem, and has received increasing attention for applications in areas such as telecommunication, automotive, and biotechnology. Current state of the art micro-assembly systems are often specialized devices and software. In this paper we present a reconflgurable assembly system designed to handle micro-parts in such a way that high precision actuation and sensing is used only in the subsystems where it is actually necessary. Aspects related to part gripping, fucturing, sensing, motion and bonding are discussed. Analysis and experiments are presented to show that this architecture can lead to a relatively low cost and flexible assembly solution.