Design and Analysis of a Parallel Robot with Flexure Hinges for Target Alignment System

Parallel manipulators has been extensively studied by virtues or its high force-to-weight ratio and wide spread applications such as vehicle or flight simulator, a machine tool and the end-effecter of robot system. However, as each limb includes several rigid joints, assembling error is demanded strictly, especially in precision measurement and microelectronics. On the other hand, compliant mechanisms take advantage of recoverable deformation to transfer or transform motion, force, or energy and the benefits of compliant mechanisms mainly come from the elimination of traditional rigid joints. In this paper, a new approach investigating the kinematics of a three translational degrees of freedom (DOF) parallel manipulator with flexure hinge is proposed. Based on characteristics of flexure hinge and topology optimal method, the kinematics of the 3-DOF parallel manipulator with flexure hinge and its control system are developed. The parallel manipulator is driven by three piezoelectric actuators and the three actuators in this mechanism are arranged according to the Cartesian coordinate system. Experiments are conducted to give some validation of the theoretical analysis.

Flexible hinge is a typical flexible element in compliant mechanisms. But in the micro area, the design of flexible Hook hinge is rare. Compared with the traditional gap-type flexure hinges, flexure hinges with curve leaf are more prone to large deformation in functions direction under the load. And through the rational design, overall error of whole body with flexure hinges with curve leaf would be reduced to a minimum. So this article uses the curve leaf as the basic unit to construct a distributed multi-leaves and large-deformation flexible Hooke hinge. In view of the hinge structure is complex and very difficult to get accurate model, the model of flexible hinge Hook is establish by pseudo-rigid method to analysis the deformation of flexible hinge Hook under pure torque load. Theoretical analysis and nonlinear finite element analysis results are very close, proved that the construction of pseudo-rigid body model is correct. The results also show that this new type of distributed multi-leaves and large-deformation flexible Hooke hinge can provide the larger two-dimensional rotating schedule, and center drift of rotation is small. So this flexible Hooke hinge is a new type of large deformation flexible Hook hinge and line with the basic rotation characteristics of Hooke hinge.

Robogami structures are employed for many purposes, including miniature parallel manipulators. Parallel manipulators require accurate joint position feedback, underlining the open problem in robogami structures for providing sophisticated feedback with 2D, fully embeddable, down-scalable, flexible sensors. Existing studies include only on-off control applications, excluding any parallel mechanism implementations and continuous proportional control signals. We implement silver inkjet printed angle sensors for the first time into a robogami structure and use this class of sensors for control. For the first time, a parallel manipulator is controlled with a 2D sensor, and printed sensors are tested for continuous control. Performances are analyzed with set-point and tracking control tasks using a paper Delta mechanism, compared with on-off control and encoder feedback control cases for better evaluation. A detailed comparison with the existing studies both for robogami parallel mechanisms and other sensor-embedded flexible hinges is provided. Encoder-like control performances are achieved in a wide range of the joint space and down to ~1 mm. RMS task space accuracy is recorded. Sources and potential improvements for the less accurate regions are stated. We conclude that printed sensors are promising for parallel mechanisms and continuous signal control applications.

A flexible parallel manipulator was proposed for high-precision pointing, which employed flexure hinges as passive joints and oriented its moving platform along all six degrees of freedom by means of six independent piezoelectric actuators. A right-circular flexure hinge with high motion accuracy and large displacement was designed based on performance analysis. The parameters of parallel mechanism were optimized by multi-objective optimization on the foundation of inverse kinematics. Moreover, workspace determination and simulation analysis were performed based on the final designed mechanism. Finally, a high-precision pointing system was built up and the performance tests had been implemented, which validated the proposed system satisfied the requirement of design targets. The concept and approach outlined can be extended to a variety of applications.

Four-dimensional printing has set the stage for a new generation of soft robotics. The applications of rigid planar parallel robotic manipulators are also significant because of their various desirable characteristics, such as lower inertia, higher payload, and high accuracy. However, rigid planar parallel robots are heavy and require different actuators and components. This study introduces a novel technique to produce a light three degrees of freedom soft parallel manipulator at a low cost, which can be stimulated easily. This technique allows researchers to customize the actuator’s design based on the requirement. The robot is made by 3D printing based on fused deposition modelling and a direct ink writing process. The design, development, and additive manufacturing of a soft parallel robot electrothermally driven by a linear silicon-based actuator and polylactic acid parts are presented. Silicon-based soft actuators replace the rigid conventional linear actuators in this study to drive the planar parallel manipulator. The actuation of actuators is conducted using simple heating compared to the conventional rigid actuator. Various heating approaches and configurations are compared and analysed to find the most suitable one for the effective linear stroke of the soft actuator. The finite element model is used to analyse the performance of the electrothermally silicon-ethanol soft actuators in ABAQUS. The kinematics of the planar parallel robotic manipulator are simulated in MATLAB to achieve its workspace. The final soft parallel robot mechanism and the active and passive links are fabricated and tested experimentally.

This paper concentrates on the development and evaluation of linear characteristics of a complex flexure hinge with high accuracy and large stiffness. The flexure hinge mechanism is used to clamp the shaft of a micropositioning stage based on the inchworm principle. Six key parameters of the flexure hinge are optimized by using finite element method. Developed flexure hinge has very good effects on the clamping and resilience that are accurate and reasonable. The evaluation result shows that the flexure hinge has excellent linear characteristic.

In this paper, a novel 3-UPU (P and U stand for prismatic and universal joints, respectively) parallel mechanism (PM) and its variant PM are proposed. Both of them have two rotational and one translational (2R1T) degrees of freedom (DOFs) without involving any parasitic motion. Mobility analysis shows that the three constraint forces provided by three limbs of the mechanism are located on the same plane and the mobile platform can translate perpendicular to this plane and rotate around any axis on it. Analysis of the mechanism’s motion characteristics demonstrates that the mobile platform outputs either pure rotation or pure translation. Moreover, the rotational axis can be fixed during the rotation process, which means no parasitic motion is involved. The causes of the motion characteristics are analyzed by the combination of an overall Jacobian matrix, a statistical method, and a geometric method. The PMs only need to translate or rotate once to move from the initial configuration to the final configuration, which allows for easy control of speeds. The relationship between mechanism parameters and singularity is analyzed. A speed control method for the PMs is proposed and a prototype is designed and made. Experiments are conducted to verify the determined motion characteristics, the speed control method, and the singularity analysis.

Design and testing of a high precision parallel manipulator with hyperbolic–elliptic flexure hinges

Photolithography is one of the core technologies of micro-nano fabrication. Recently, lithography technology is applied to diverse field of technologies. These technologies include MEMS (micro electro mechanical system) devices, FPD (flat panel display), and semiconductor industry. When it comes to the typical exposure process of lithography technology, photomask costs is occupying large portion of the optical system. So, how to reduce the cost of the mask and employing maskless lithography technology has become an important issue to engineers. Although there being both advantages and disadvantages, maskless lithography is a receiving substantial attention from engineers in the fileds of micro-nano fabrication. With the development of technology, low cost, flexibility, efficiency in the fabrication of device are in high demand in maskless lithography technology. How to generate line/space patterns is gaining considerable attention in terms of maskless lithography exposure process. In order to achieve the accurate alignments of numerous optical heads within a reasonable amount of tack time, installing autonomous position align micro parallel manipulator system in each optical heads required. Applied parallel manipulator that consists of four 2-DOF (degree of freedom) decoupled actuator gives chances to provide 6-DOF independence motion, and has strength in high accuracy. It is thus, this parallel manipulator is suitable for the experiment. This paper covers the follows: First, we reported the DMD (Digital Micro mirror Device)-based makless lithography system to introduce spot array method in maskless digital exposure process. Second, applying a redundant parallel micro manipulator and analyzing kinematic characteristic of the 4-[PP]PS parallel manipulator is described. After that, comparing benefits and drawbacks of 4-[PP]PS parallel and 4-DOF serial manipulator is covered. Third, proposing a suitable error model of the system and applying the genetic algorithm to alignment spot array concerning position correction. Finally, we designed experiment which has vision sensor and align unit to verify positioning algorithm. Simulation and experimental result will be shown with the regard to parallel manipulator can find the optimal solution based on genetic algorithm and carry out the problem of spot array alignment by reducing the position error of the system.

A novel flexure hinge named right circular corner filleted half hybrid flexure hinge was advanced. Based on the Castigliano second theorem, the compliance formulas of the novel flexure hinge were formulated. The theoretical calculations and the finite element simulations were performed simultaneously, the similar results were obtained which indicated the correctness of the compliance formulas. The influence of the geometric parameters of the novel flexure hinge on its performance was analysed. Compared with right circular corner filleted double hybrid flexure hinge, the compliance and sensitivity to the load of the novel half hybrid flexure hinge were better than that of the right circular corner filleted double hybrid flexure hinge. All of the above analysis results indicated the novel flexure hinge are more suitable for application in the compact structure and large displacement.

A three degree of freed parallel micromanipulator is presented.The DOF of parallel manipulator is analyzed by the screw theory, the driven number is gotten. The kinematics solutions are analyzed using the vector theory, as a result, the velocity of a movable platform are derived. Based on Jacobian matrix, the forward and inverse kinematic singular configuration of the parallel micromanipulator is also studied. The results show that sensitivity parameters existed in Jacobian matrix affect the relation between the input and the output of the micromanipulator, the vector space method is simple and convenient in analyzing the singularity of parallel mechanisms. The simulation results verified that the robot has the tiny displace, and the kinematics parameters of the robot can be conveniently acquired, so the study provides theoretical bases for the robot control and performance improvement.

In this paper we present the kinematic and dynamic analysis of a parallel architecture manipulator with linear actuators, consisting of two 3-RRPS mechanisms through the screw theory and the principle of virtual work, respectively. The equations of input / output speed and acceleration are obtained by applying the Klein form of the Lie algebra. In addition, the generalized forces of the mechanism are determined by combining the above theory with the principle of virtual work. Finally, we present a case of study; the numerical results are compared with simulations using ADAMS software.

We have developed a high performance force display system with a parallel manipulator. The manipulator is composed of a parallel mechanism with direct drive linear servo actuators. The mechanism is called a fixed linear type parallel mechanism. Since the actuators are fixed on the base, the high speed motion of the manipulator is possible. In addition, the mechanism has high load capacity and back derivability. These characteristics lead to a high performance force feedback control. We describe the design policy, the analysis of the operation area, the prototyping and control of the parallel manipulator.

There exists a duality relationship between a twist and a wrench in the dynamics of a mechanism or a multi-body system. Using this relationship, the coordinate-free expressions for the dynamic analysis of multi-loop mechanisms is derived. In the analysis, a Jacobian matrix expressing the relationship among loops is defined, and it is clarified, by using this matrix, that both twists and wrenches can be easily analyzed based on the duality relationship among them. A parallel mechanism having connecting chains with loops is also analyzed, and it is shown that the same procedure can be applied to a parallel mechanism with connecting chains, each loop of which has a motion space that is different from that of the mechanism.

Workspace Analysis of the 4RRR Planar Parallel Manipulator with Actuation Redundancy