Passive Compliant Mechanisms Research Articles

Design and analysis of a wall-climbing robot with passive compliant mechanisms to adapt variable curvatures walls

AbstractMotivated by practical applications of inspection and maintenance, we have developed a wall-climbing robot with passive compliant mechanisms that can autonomously adapt to curved surfaces. At first, this paper presents two failure modes of the traditional wall-climbing robot on the variable curvature wall surface and further introduces the designed passive compliant wall-climbing robot in detail. Then, the motion mechanism of the passive compliant wall-climbing robot on the curved surface is analyzed from stable adsorption conditions, parameter design process, and force analysis. At last, a series of experiments have been carried out on load capability and curved surface adaptability based on a developed principle prototype. The experimental results indicated that the wall-climbing robot with passive compliant mechanisms can effectively promote both adsorption stability and adaptability to variable curvatures.

A Self-Rotary Aerial Robot With Passive Compliant Variable-Pitch Wings

Inspired by maple seeds, the self-rotary winged aerial robots reflect the advantages of both multi-rotor aircraft and fixed-wing robots. However, their self-rotating speed is related to the takeoff weight, which may affect their application and flight stabilization. To provide a practical and feasible solution, this work proposes a passive compliant variable-pitch mechanism on the self-rotary winged aircraft without requiring extra actuators. Depending on the weight of the payload, the pitching angle of the wings can be passively varied to minimize the increase in the rotating speed and enhance attitude stabilization ability. Besides, an adaptive attitude controller is also designed to address the challenges in attitude stabilization, which are caused by parameter uncertainties and the variable pitching angle. To elaborate on the design and fabrication of the prototype, necessary identification experiments are arranged to find the relationship of pitching angle, thrust generation, power draw, and rotating speed. The experimental findings indicate the proposed robot with optimal pitch angles achieves around 56.8% more power loading than using propellers directly, from 4.4 to 6.9 g/w. The combination of the passive compliant mechanism and adaptive controller improves flight performance from 0.16 to 0.08 meters (mean of absolute translational error).

Optimization of Variable Stiffness Joint in Robot Manipulator Using a Novel NSWOA-MARCOS Approach

Robots and robotic systems have become an inevitable part of modern industrial settings. Robotics systems are being introduced for various household services as well. As the interactions between the workspace of robots and humans increases, there is an increased likelihood of unintended harm being caused by the robots to humans due to collisions or abrupt contact. To mitigate this, active and passive compliant mechanisms must be introduced in these systems. In this study, a design optimization case study is carried out for the optimization of a passive compliance mechanism achieved with variable stiffness joints realized by the use of permanent magnets. Three design parameters of the systems, namely, inner stator width, outer stator width, and magnet height, are considered. The objective is to minimize the weight and maximize the maximum torque. A nature-inspired metaheuristic hybridized with a multi-criteria decision-making method is introduced to achieve this. The Non-dominated Sorting Whale Optimization Algorithm (NSWOA) is used for Pareto optimal front generation and MARCOS (Measurement of Alternatives and Ranking according to COmpromise Solution) is applied to extract the best feasible solution from the Pareto front. We observed 1.8% and 41% improvements as compared to the previous known best design and original design, respectively.

Design of Novel End-effectors for Robot-assisted Swab Sampling to Combat Respiratory Infectious Diseases.

The COVID-19 outbreak has caused the mortality worldwide and the use of swab sampling is a common way of screening and diagnosis. To combat respiratory infectious diseases and assist sampling, robots have been utilized and shown promising potentials. Nonetheless, a safe, patient-friendly, and low-cost swabbing system would be crucial for the practical implementation of robots in hospitals or inspection stations. In this study, we proposed two recyclable and cost-efficient end-effector designs that can be equipped at the distal end of a robot to passively regulate or actively sense the force exerted onto patients. One way is to introduce passive compliant mechanisms with soft material to increase the flexibility of the swabbing system, while the other way is utilizing a force-sensing gripper with embedded optoelectronic sensors to actively sense the force or torque. The proposed designs were modelled computationally and tested experimentally. It is identified that the passive compliant mechanisms can increase the flexibility of the swabbing system when subjected to the lateral force and mitigate the vertical force resulted from buckling. The lateral force range that the force-sensing gripper can detect is 0-0.35 N and the vertical force range causing buckling effect that can be sensed by gripper is 1.5-2.5 N.

Design and experiment of remote handling motor replacement device based on passive compliant mechanism

Design and experiment of remote handling motor replacement device based on passive compliant mechanism

Efficient Insertion of Multiple Objects Parallel Connected by Passive Compliant Mechanisms in Precision Assembly

This paper proposes an efficient strategy to simultaneously insert multiple objects, which are parallel connected by passive compliant mechanisms, in precision assembly. The distinctions of this task include: each object is held compliantly; multiple objects are parallel connected to a manipulator; not all the peg-in-hole has the same insertion condition; and high accuracy is required for each insertion. This configuration can provide sufficient compliance and improve insertion efficiency for massive precision assembly. We model the relationship between the state and force of a single compliant mechanism, and analyze the horizontal compliance of parallel mechanisms. Based on the model, with a fitting and optimization method the states of all but one compliant mechanisms are acquired from microscopic views and the remaining states are optimized with resultant forces provided by a force sensor. To efficiently plan the parallel insertion, we propose a strategy to horizontally compensate according to the resultant force and the horizontal compliance, and to vertically insert based on the insertion ratio expectation, the horizontal offsets of each individual insertion, and the horizontal force. Experiments are carried out to demonstrate the validation of the proposed method.

Development of a Passive Compliant Mechanism for Measurement of Micro/Nanoscale Planar 3-DOF Motions

This paper presents the design, optimization, and computational and experimental performance evaluations of a passively actuated, monolithic, compliant mechanism. The mechanism is designed to be mounted on or built into any precision positioning stage, which produces three degree-of-freedom (3-DOF) planar motions. It transforms such movements into linear motions, which can then be measured using laser interferometry-based sensing and measurement techniques commonly used for translational axes. This methodology reduces the introduction of geometric errors into sensor measurements, and bypasses the need for increased complexity sensing systems. A computational technique is employed to optimize the mechanism's performance, in particular, to ensure the kinematic relationships match a set of desired relationships. Computational analysis is then employed to predict the performance of the mechanism throughout the workspace of a coupled positioning stage, and the errors are shown to vary linearly with the input position. This allows the errors to be corrected through calibration. A prototype is manufactured and experimentally tested, confirming the ability of the proposed mechanism to permit measurements of 3-DOF motions.

Design of a compensation mechanism for an active cardiac stabilizer based on an assembly of planar compliant mechanisms

In this paper we present the design of a compact active cardiac stabilizer based on planar compliant mechanisms and piezoelectric actuators. Considering an assembly of planar manufactured structures helps to simplify the manufacturing process and may increase the compactness. Parallel architectures constitute interesting solutions for their intrinsic stiffness properties, but in a planar configuration parallel manipulators often exhibit kinematic singularities. Two design approaches for planar parallel compliant mechanisms are presented in this paper. One design approach consists in designing a passive compliant mechanism in a configuration close to the singularity by introducing some asymmetries during the manufacturing process. The second design approach consists in taking advantage of the singularities of parallel manipulators to obtain non-trivial solutions. The new proposed active stabilizer, composed of planar compliant mechanisms, is introduced and its performances are discussed.

Spring-joint method for topology optimization of planar passive compliant mechanisms

There is seldom approach developed for the initial topology design of flexure-based compliant mechanisms. The most commonly-used approaches, which start with an existing rigid-body mechanism, do not consider the performances between different topologies. Moreover, they rely heavily on the rigid-body topology, therefore limit the diversity of compliant mechanisms topology. To obtain the optimal initial topology of such mechanisms directly from problem specifications without referencing to the existing mechanism topologies, a spring-joint method is presented for a restricted class of the serial passive flexure-based compliant mechanisms, which are the building blocks of parallel compliant mechanisms. The topology of the compliant mechanisms is represented by a serial spring-joint mechanism(SSJM) that is a traditional rigid-body mechanism with a torsional spring acting on each joint, and is described by position vectors of the spring-joints. A simplified compliance matrix, determined by the position vectors, is used to characterize the tip of the SSJM kinematically, and is optimized to ensure the desired freedoms of the compliant mechanisms during optimization. The topology optimization problem is formulated as finding out the optimal position of the spring-joints in a blank design domain with an objective function derived from the simplified compliance matrix. In design examples, syntheses of the compliant mechanisms with both single freedom and two decoupled freedoms are presented to illustrate the proposed method. The proposed method provides a new way for the initial design of flexure-based compliant mechanisms.

Monolithic design of a compliant template orientation stage for step imprint lithography

The parallel surface contact between a template and a wafer is of critical importance for pattern fidelity in step imprint lithography. The passive compliant stage, which has a much simpler structure than an active control one, is an effective orientation-adjusting mechanism. For a perfect passive compliant stage, the orientation-adjusting process should bring about the smallest possible additional lateral motion to maintain the overlay precision. In the present paper, based on the analysis of a compliant wafer stage and the influence of the rotation axis on position shift, a monolithic template orientation stage with four groups of passive compliant mechanisms is proposed to satisfy the above requirements. This compliant template orientation stage can be regarded as two four-bar linkages that interfere with each other, with the connecting line of two flexible hinges in each group passing through the centre of the template, ensuring that the rotation axis is located in the centre of the template during the whole orientation-adjusting process. The performance of the designed compliant template orientation stage is researched using the finite element analysis method and experiments. The results indicate that this compliant template stage can ensure the parallel surface contact between a template and a wafer while minimizing relative lateral motion during the imprinting process.

家庭用コンテナケース運搬ロボットにおける機械的柔軟性を活用したシステム構成法の提案と実証

This paper proposes a system configuration method to realize a robot system which can perform daily-use object storage and management service in a living space. In the method, compliant mechanisms are utilized proactively to overcome position/posture errors and deviations in measurement or control phases. To validate the proposed system configuration method, we developed a home-use container transfer robot that is installed with (1) robust container handling mechanisms implemented by crank shafts and (2) passive compliant mechanisms for horizontal and inclination misalignment. The robot was integrated with a container position measurement system to perform experiments. Experiments confirmed that a robust container transfer motion can be realized without complex feedback measurement and control processes. Several key design points are also described to leverage mechanical compliance.

Wheel-terrain Geometric Contact Angle Estimation of All-terrain Mobile Robots

摘要: 研究全地形移动机器人在不平坦地形中轮－地几何接触角的实时估计问题. 本文以带有被动柔顺机构的六轮全地形移动机器人为对象, 抛弃轮－地接触点位于车轮支撑臂延长线上这一假设, 通过定义轮－地几何接触角 δ 来反映轮－地接触点在轮缘上位置的变化和地形不平坦给机器人运动带来的影响, 将机器人看成是一个串－并联多刚体系统, 基于速度闭链理论建立考虑地形不平坦和车轮滑移的机器人运动学模型, 并针对轮－地几何接触角 δ 难以直接测量的问题, 提出一种基于模型的卡尔曼滤波实时估计方法. 利用卡尔曼滤波对机器人内部传感器的测量值进行噪声处理, 基于机器人整体运动学模型对各个轮－地几何接触角进行实时估计, 物理实验数据的处理结果验证了本文方法的有效性, 从而为机器人运动学的精确计算和高质量的导航控制奠定了基础. 关键词: 全地形移动机器人 / 轮－地几何接触角 / 运动学建模 / 卡尔曼滤波

構造的特異性を利用した零／極高剛性を実現するトルク伝達機構とそのロボット関節への応用

To introduce a passive compliant mechanism for robot joints is an effective way for impact absorption. However, because robot joints also require high torque transmission characteristic, the simultaneous implementation of stiffness and softness is a significant issue. In this paper, we develop a torque transmission mechanism with nonlinear passive stiffness that realizes from zero to extremely high stiffness based on mechanical singularity. The analysis of nonlinearity of the stiffness is established and the experimental evaluations are shown. A four-legged robot with the proposed mechanism is designed and the effectiveness of high nonlinearity of the proposed mechanism is illustrated.