Parallelogram Mechanism Research Articles

Development and Testing of a Dual-Driven Piezoelectric Microgripper with High Amplification Ratio for Cell Micromanipulation

Cell micromanipulation is an important technique in the field of biomedical engineering. Microgrippers play a crucial role in connecting macroscopic and microscopic objects in micromanipulation systems. However, since the operated biological cells are deformable, vulnerable, and typically distributed in sizes ranging from micrometers to millimeters, it poses a huge challenge to microgripper performance. To solve this problem, this paper develops a dual-driven piezoelectric microgripper with a high displacement amplification ratio, large stroke, and parallel gripping. By adopting modular configuration, three kinds of flexure-based mechanisms, including the lever mechanism, Scott–Russell mechanism, and parallelogram mechanism are connected in series to realize three-stage amplification, which effectively makes up for the shortage of small output displacement of the piezoelectric actuator. At the same time, the use of the parallelogram mechanism also isolates the parasitic rotation movement, and realizes the parallel movement of the gripping jaws. In addition, the kinematics, statics, and dynamics models of the microgripper are established by using the pseudo-rigid body and Lagrange methods, and the key geometric parameters are also optimized. Finite element simulation and experimental tests verify the effectiveness of the developed microgripper. The results show that the developed microgripper allows an amplification ratio of 46.4, a clamping stroke of 2180 μm, and a natural frequency of 203.1 Hz. Based on the developed microgripper, the nondestructive micromanipulation of zebrafish embryos is successfully realized.

Design and Experiment of an Independent Leg-Type Chassis Vehicle Attitude Adjustment System

In response to the current low work efficiency of soil ridge-working machinery, as well as its poor stability, passability, and adaptability, this paper designs an independent leg-type working platform that can autonomously adjust its vehicle attitude through LiDAR scanning in a soil ridge-working environment. The platform, in terms of its mechanism and structural design, adopts dual parallelogram mechanisms, dual lead screw mechanisms, and independent column leg mechanisms, with a maximum adjustable ground clearance of 107 mm and a maximum wheelbase adjustment of 150 mm. A gyroscope is mounted at the center of the platform for attitude adjustment, ensuring the accurate data collection of the ultrasonic ranging module. Moreover, the platform adopts an adaptive adjustment method based on vehicle attitude and soil ridge shape parameters, obtaining soil ridge parameters through LiDAR and combining ultrasonic ranging module data with stepper motor pulse signals to obtain the absolute vehicle attitude parameters, using first and second linear regression methods to adjust the vehicle attitude and other working parameters. A prototype was also created, and the test data from the soil obtained through experiments show that, after leveling with the gyroscope leveling algorithm, the average value of the pitch angle is up to 0.6154°, and the average value of the roll angle is up to 0.9989°, with the maximum variance of the pitch angle being 0.0474° and the maximum variance of the tilt angle being 0.1320°. After the ultrasonic ranging module data are filtered by the Kalman filter, the maximum variance is 0.0304, and after applying the final fusion algorithm, the maximum variance is only 0.0085. The LiDAR measurement width value deviates from the actual width value by no more than 1.0 cm, and the LiDAR measurement height value deviates from the actual height value by no more than 1.0 cm. The platform’s actual adjusted width deviates from the actual soil ridge width by no more than 2.0 cm, and the platform’s actual adjusted height deviates from the actual soil ridge height by no more than 1.2 cm. This platform can improve the passability, adaptability, and stability of agricultural machinery in soil ridge work and provide technical references for subsequent related research.

Design, computational analysis and experimental study of a high amplification piezoelectric actuated microgripper

Increasing applications of compliant microgripper demands flexibility in working with a wide range of micro-objects which requires a large workspace, high precision motion, low parasitic motion, and satisfactory bandwidth control. To meet the requirement of pick and place manipulation tasks, a high amplification piezoelectric actuated microgripper is proposed and investigated in this paper. The high amplification of the microgripper is achieved using a compound amplifier. The compound amplifier is assisted to magnify the embedded piezoelectric actuator’s displacement. Two cascaded lever-type mechanisms are symmetrically connected with a bridge-type mechanism and form a three-stage amplification mechanism-based compound amplifier. Further, the four-bar parallelogram mechanisms are integrated with the third-stage displacement amplification mechanisms to linearize the output motion of the microgripper jaws. The characteristics of the microgripper were evaluated by computational analysis and validated using experimental investigations. Further, the design parameters are identified from the geometrical model of the individual displacement transmission mechanisms to perform a response surface optimization on the configured mechanism by the computational method. The design optimization of the microgripper resulted in a high displacement amplification ratio with a large workspace. The experimental investigations show that the designed microgripper is capable of achieving a high displacement amplification ratio of 34.5 and a total output displacement of 529.4 μm. Further, the characteristics of the microgripper such as motion resolution, and parasitic motion indicate that it will be able to perform high-precision micro-object grasping/releasing tasks.

Design, modeling, and control of a long stroke compliant tip-tilt-piston micropositioning stage driven by voice coil motors.

In this paper, a long-stroke parallel compliant tip-tilt-piston micropositioning stage driven by voice coil motors (VCMs) is proposed. The stage is equipped with three sets of driving arms, which include a spherical hinge, VCM, and parallelogram guide mechanism, evenly spaced at 120° intervals. The spherical hinge is composed of orthogonal leaf-spring beams, and the VCM is embedded into the parallelogram mechanism to form a compact design. The compliance matrix method and the geometric method facilitated the determination of compliance in all six degree-of-freedom directions of the spherical hinge and the derivation of kinematic equations for decoupling the motion of the stage. In addition, finite element analysis was utilized to determine the maximum stroke and stress of the stage. To validate the proposed design, a stage prototype was constructed and subjected to experimental testing. Furthermore, a feedback controller was designed, integrating proportional integral controller, notch filter, and sliding mode controller feedforward. The experimental results indicate that the stage can achieve a long stroke of ±50.75 mrad × ±44.2 mrad × ±4.425mm, with the natural frequencies in the three-axis direction of 22.3 × 25.5 × 25.5Hz3. In addition, the maximum relative tracking error was maintained below 5.25%, highlighting the effectiveness of the control technique in achieving a high tracking performance.

Амплитудно-частотные характеристики виброзащитной системы сиденья с трехсегментной статической силовой характеристикой и участком квазинулевой жесткости

Vibration protection for heavy equipment operators is important. Exposure to vibration is harmful to health. Vibration protection seats are used for protection. Reliable passive systems with quasi-zero stiffness are promising. For the developed design of the seat on the basis of parallelogram mechanism, spring, cable and rollers, the study of vibration-protective properties is carried out. The design scheme has been developed, key parameters have been selected, and their study on vibration protection parameters has been carried out. The static force response was approximated by three linear segments with a horizontal mean. The known dynamic model describing forced oscillations of the mass was used. The displacement of the base was given by a harmonic function. Vibration protection systems with three-segment and with one-segment static force response were compared. The comparison was carried out in terms of transmission coefficients, accelerations and suspension displacement. The results of the computational experiment are presented in the form of graphs: amplitude-frequency characteristics in the form of transmission coefficients in acceleration and displacement, at different amplitudes of base vibrations, damp-ing and stiffness coefficients. Dependences of average values of transmission coefficients in the investigated frequency range are given. Vibration damping is effective when the maximum suspension travel does not exceed the middle section of the static characteristic. The most effective vibration damping, according to the average value of the acceleration transfer coefficient, is achieved at minimum, and for a single-segment characteristic — zero values of the stiffness coefficient. The presence of extreme segments in the characteristic significantly increases the average values of the accelera-tion and displacement transfer coefficients of the suspension. Seat vibration protection systems in real conditions should have a limitation of suspension displacement for ergonomic reasons. The values of the stiffness coefficients of the extreme parts of the static force response, according to the criterion of minimizing the average value of the acceleration transfer coefficient, should be minimized. To substantiate the optimal values of the stiffness coefficients of the extreme sections of the characteristic and viscous friction coefficients, it is advisable to conduct additional studies under step and stochastic impacts.

Design and movement mechanism analysis of a multiple degree of freedom bionic crocodile robot based on the characteristic of “death roll”

AbstractThis paper introduces a multi‐degree of freedom bionic crocodile robot designed to tackle the challenge of cleaning pollutants and debris from the surfaces of narrow, shallow rivers. The robot mimics the “death roll” motion of crocodiles which is a technique used for object disintegration. First, the design incorporated a swinging tail mechanism using a multi‐section oscillating guide‐bar mechanism. By analyzing three‐, four‐, and five‐section tail structures, the four‐section tail was identified as the most effective structure, offering optimal strength and swing amplitude. Each section of the tail can reach maximum swing angles of 8.05°, 20.95°, 35.09°, and 43.84°, respectively, under a single motor's drive. Next, the robotic legs were designed with a double parallelogram mechanism, facilitating both crawling and retracting movements. In addition, the mouth employed a double‐rocker mechanism for efficient closure and locking, achieving an average torque of 5.69 N m with a motor torque of 3.92 N m. Moreover, the robotic body was designed with upper and lower segment structures and waterproofing function was also considered. Besides, the kinematic mechanism and mechanical properties of the bionic crocodile structure were analyzed from the perspectives of modeling and field tests. The results demonstrated an exceptional kinematic performance of the bionic crocodile robot, effectively replicating the authentic movement characteristics of a crocodile.

A novel method to enhance the accuracy of parameter identification in elasto-geometrical calibration for industrial robots

Elasto-geometrical calibration is crucial for enhancing the absolute accuracy of robots in machining operations through the identification and compensation of parameter errors. However, the presence of inconsistent measurement units and improper selection of measuring poses can result in the ill-conditioned identification matrix (ICIM) issue, consequently impacting the accuracy of parameter identification. This paper introduces a novel method to tackle this challenge. Initially, an elasto-geometrical error model is developed based on the orientation-independent measurements (OIM), efficiently reducing the impact of mismatched positions and orientations on the ICIM problem. Subsequently, a PSO-SFFS algorithm is proposed to optimize the measurement configurations and minimize the influence of measurement noise. Furthermore, the incorporation of screw theory and the consideration of parallelogram mechanisms enhance the precision and comprehensiveness of the error model. Subsequent to the development of the error model, calibration comparison experiments are conducted on an industrial robot. Both simulation and experimental results validate the effectiveness of the proposed method in improving parameter identification accuracy.

Design and Control of a Flexure-Based Dual Stage Piezoelectric Micropositioner

In the field of advanced manufacturing technology, there is a growing need for high-precision micro/nano positioners. The traditional single stage actuated positioners have encountered performance limitation in achieving longer travel range and higher precision. This motivates us to develop a novel dual stage piezoelectric-actuated micropositioner presented in this paper. The micropositioner incorporates displacement amplification mechanisms to overcome the limited range of piezoelectric actuators. Design considerations such as flexure characteristics and material selection are discussed, and structural analysis is performed using finite element analysis (FEA). For precise positioning, the dual stage control strategy is investigated and compared with the conventional proportional-integral-derivative (PID) single stage control method. In the proposed positioner, a combination of parallelogram and bridge mechanisms is utilized. The bridge mechanism works to amplify the piezoelectric actuator displacement output. The parallelogram mechanism, integrated within the system, helps mitigate resonance modes and contributes to the achievement of linearized motion. The characteristics of the micropositioner were evaluated using analytical modelling and FEA. Multiple analysis was used to optimise the positioner’s design parameters. Furthermore, experimental studies were carried out to validate the characteristics of the micropositioner performance in terms of achievable output travel range and sustained positioning accuracy.

A Lie group variational integrator in a closed-loop vector space without a multiplier

Abstract. As a non-tree multi-body system, the dynamics model of four-bar mechanism is a differential algebraic equation. The constraints breach problem leads to many problems for computation accuracy and efficiency. With the traditional method, constructing an ODE-type dynamics equation for it is difficult or impossible. In this exploration, the dynamics model is built with geometry mechanic theory. The kinematic constraint variation relation of a closed-loop system is built in matrix and vector space with Lie group and Lie algebra theory respectively. The results indicate that the attitude variation between the driven body and the follower body has a linear recursion relation, which is the basis for dynamics modelling. With the Lie group variational integrator method, the closed-loop system Lagrangian dynamics model is built in vector space, with Legendre transformation. The dynamics model is reduced to be the Hamilton type. The kinematic model and dynamics model are solved using Newton iteration and the Runge–Kutta method respectively. As a special case of a crank and rocker mechanism, the dynamics character of a parallelogram mechanism is presented to verify the good structure conservation character of the closed-loop geometry dynamics model.

Design and implementation of a field robot using a parallelogram mechanism.

To meet various industrial requirements such as ease of motion, scalability, and cost efficiency, it is necessary to innovate the design of robotic platforms. In this research, a novel approach, from mechanical design to control implementation, is introduced for launching a robotic platform using a parallelogram mechanism. First, a reverse engineering process is applied, progressing from kinematics to dynamics. Then, several mechanical computations are conducted to ensure the structural stability of the robot framework. Subsequently, the dynamic performance of the system is analyzed, focusing on the driving torque and moments in each link. Additionally, the electrical design and transfer function of each joint are identified to ensure practical execution. To validate the effectiveness and feasibility of the design, both numerical simulations and experimental tests are performed. Theoretical results show the dynamic response of the proposed method, particularly in terms of the driving moments of the robotic joints. In real-world tests, various trajectories, such as different rectangular paths, are demonstrated to showcase the robot's capabilities. From these results, it is clear that the proposed approach is both feasible and applicable in practical scenarios.

Development and Test of a Multimode Piezomotor With Active Contact Force Adjusting

Piezomotors have been widely used for motion generation with long stroke and fine resolution, where stick-slip mode features a high motion velocity but a low load capacity, inchworm mode has a high load capacity but a low motion velocity, and scan mode is able to realize super-high resolution but less travel range. Combining these motion modes to achieve a well-rounded piezomotor is challengeable but significant. In this study, a piezomotor with multiple motion modes is proposed. A compliant mechanism with a parallelogram mechanism and lever-type amplifiers is designed to realize various motion modes and adjust the contact force, which has a significant impact on motion performance. To prevent the backward motion and slippage during motion, two power-function based driving signals are designed and analyzed for stick-slip mode and inchworm mode, respectively. A prototype of the designed piezomotor was fabricated to validate the feasibility. According to the experiment results, the maximum motion velocity is 3.24 mm/s, the load capacity is 7.85 N, and the most fine displacement resolution is 10 nm. The proposed methodology is applicable to other types of multi-mode piezomotors.

A novel robotic system enabling multiple bilateral upper limb rehabilitation training via an admittance controller and force field

Patients with hemiplegia are usually restricted to performing general bilateral activities of daily life (gbADLs). Bilateral training has been verified to contribute to the rehabilitation of physical functions. Although robotic systems are gradually being employed in the field of rehabilitation, few studies have performed simulations with regards to gbADLs for training. Therefore, a novel end-effector bilateral rehabilitation robotic system (EBReRS) for the upper limb is developed in this article for the task rendering of gbADLs, in which the gbADL-corresponding workspace is obtained via modularly designed bilateral parallelogram mechanisms. In addition, the interaction rendering of multiple bimanual modes (uncoupled, trans-soft-coupled, trans-semi-coupled, and rotation-coupled) is achieved by implementing the admittance model, the inner force field between robotic end-effectors, and the outer force field distributed around. Experiments of the proposed four rehabilitation training modes were carried out on the healthy subject, with the results showing a feasible method of the EBReRS in the simulation of multiple bimanual coordinated rehabilitation training tasks. In the future, the constructed EBReRS is expected to be exploited for home rehabilitation as a coordinated training device.

Design of a two-stage compliant asymmetric piezoelectrically actuated microgripper with parasitic motion compensation

The parasitic motion of microgripper jaws affect clamping accuracy. The parallelogram mechanism (PM) is often used as the last-stage of the multi-stage amplification mechanisms (AMs) because of its parallel clamping characteristics. However, the PM traditionally used in multi-stage AMs is asymmetrically stressed, which will affect its parallel clamping accuracy. Based on this, a PM with symmetrical forces is designed. The paper addresses the issue of parasitic motion in microgripper jaws and its impact on clamping accuracy, which is a relevant concern in micro-scale manipulation systems. The design of a symmetrically stressed PM for use in a two-stage asymmetric microgripper is a novel contribution to the field. Based on the minimum potential energy principle and the Castigliano's second theorem, the mechanical modeling of the mechanism's parasitic displacement, magnification and parallel clamping accuracy is carried out. Comparing the mechanical model, finite element analysis (FEA) and experimental measurement results, the values given by the three different methods are close. The method given in this paper to improve the clamping accuracy of the mechanism is also applicable to similar compliant mechanisms.

Improved Tilting Method for Automobile Mass Center Measurement Based on Simulation Analysis

The Tilting Method(TM) is applied to measure the automobile mass center position widely for simple principles and easy operations. However, the TM has some problems, such as inaccurate calculation of tire force point and large tilting angle of the vehicle, so the Improved Tilting Method (ITM) is proposed in this paper. In the process of running ITM, the tire force direction is always straight up, so the friction and other adverse factors are less than that in TM. ITM applies a combined parallelogram mechanism to keep the supporting plates horizontal. In this research, we study the ITM measurement process by simulation analysis. The research results show that the design scheme and the equipment movement outcomes prove the feasibility and practicability of the ITM.

Design and implementation of shape‐adaptive and multifunctional robotic gripper

AbstractThis paper presents a multifunctional underactuated two fingered adaptive grippers for grasping a wide range of objects in different working scenarios. Two layered‐based novel multifunctional gripper design is proposed by stacking a multijointed closed‐chain mechanism over a multijointed double parallelogram mechanism to achieve a maximum number of grasping techniques. The multijointed closed‐chain mechanism is employed to perform power, shape‐adaptive grasping, and a multijointed double parallelogram mechanism is used to perform scooping, parallel, and pinch grasping. For stable shape‐adaptive/power grasping, the proposed design allows more contact points between the object and the contact surface of fingers as compared to previous gripper mechanisms. Moreover, a complete mathematical model relating the contact forces at the links of each finger to the linear actuation force and spring torque is developed to conduct stability analysis of the proposed gripper design. Finally, simulations and several experiments are performed using real objects in a reconfigurable environment to demonstrate and validate the stable grasping capabilities of the proposed gripper.

Optimization of design parameters of the vibration protection system of a motor grader seat with quasi-zero stiffness

BACKGROUND: Vibrations occurring during operation of land transport-technological machines deteriorate the quality of control, reduce the productivity of the work performed, adversely affect the health of machine operators. In order to reduce the impact of vibrations on the operators, vibration protection systems of the cab and seat are used.
 AIMS: For practical application of the developed design of the passive vibration protection system of the motor grader operators seat on the basis of a parallelogram mechanism, tensile spring, cable and rollers, it is necessary to develop an algorithm for optimizing the values of design parameters.
 METHODS: The mean square value of seat acceleration in a stationary reference frame, determined as a result of simulation of the motor grader motion over a set of stochastic microprofiles of the support surface with various characteristics and velocities, was used as an optimization criterion. Comprehensive simulation mathematical model of a motor grader with cabin vibration protection supports and vibration protection system of a seat was used. All parameters of the optimization algorithm and model were divided into fixed, random and varying ones. The latter include a number of dimensions of the parallelogram mechanism of the seat vibration protection system, the coefficient of viscous friction of the mechanisms shock absorber, the height of the quasi-zero stiffness zone. The dependence of the criterion on the design parameters of the seat vibration protection mechanism, which has an implicit pattern and is determined by means of a simulation mathematical model, served as the target function. Boundary conditions were imposed on a number of parameters to ensure the operability of the mechanism, manufacturability of its parts as well as ergonomic considerations. Optimization of the values of the varying parameters was performed with the simplex method. At the same time, a part of the parameters unambiguously influencing the value of the target function was preliminarily maximized or minimized within the boundary ranges.
 RESULTS: An algorithm for assignment and optimization of design parameters of the vibration protection system of a motor grader seat with quasi-zero stiffness is developed, one of the key features of which is the possibility to adjust the vibration protection system of the seat to the weight of the current operator. Examples of algorithm application are given.
 CONCLUSIONS: The algorithm makes it possible to determine the optimal values of design parameters of the seat vibration protection system based on a parallelogram mechanism such as: the dimensions of the parallelogram mechanism, including the attachment points of rollers and cable, the coefficient of tensile spring stiffness, the coefficient of viscous friction of a shock absorber, the parameter of adjusting the mechanism to the weight of the current operator. The key feature of the developed vibration protection system and the optimization algorithm of its design parameters is the possibility of adjustment to the weight of the current operator.

Design and mechanical modeling of high-magnification and low-parasitic displacement microgripper with three-stage displacement amplification

The common point of multi-stage displacement amplification mechanisms (DAMs) is that the output end of the upper-stage DAM is connected to the input end of the next-stage DAM. Therefore, the input stiffness of the next-stage DAM will have an impedance effect on the output displacement of the upper-stage DAM. Based on this, the paper introduces a three-stage amplification microgripper, which is driven by a piezoelectric actuator. The three-stage DAM is composed of a compound rhombic mechanism, a bridge mechanism and two parallelogram mechanisms. Based on Cartesian second theorem and flexure beam theory, the mechanism's displacement magnification model, input force and output force relationship model, force-displacement relationship model, input stiffness model and parasitic displacement compensation model are established. The correctness of mechanical modeling is verified by simulation analysis and experiments. The results show that the mechanical model has high prediction accuracy.

Energy intensity of the device for lifting the soil of the machine for pre-sowing soil preparation and sowing

The subject of the study is the process of the machine for preparing the soil and sowing sunflower and corn seeds. The technological process of operation of the machine with installed guide passive rotating flat discs with ridges seeding apparatus, seed line, furrow, rotor, separating grid, parallelogram mechanism, spring, plumeshare is described. Studies have been carried out at reducing the energy consumption of the device for lifting the soil by installing support drums between the guide disks, the radius of rotation of which is less than the radius of the disks. It is determined that in order to obtain the minimum values of the kinematic parameter at the lowest energy consumption, the radius of the guide discs must be chosen, based on the conditions of the depth of seed embedding in the soil, the smallest. With an increase in the coefficient of adhesion, the traction resistance of the working section of the tillage machine increases more significantly than the kinematic parameter. Therefore, in order to reduce the traction resistance, it is necessary to strive to reduce the coefficient of adhesion of the drum with the soil.

Deployable Parallelogram Mechanism and Constrained Bendable Segment for Flexible Robot Toward Transoral Procedures

Deployable Parallelogram Mechanism and Constrained Bendable Segment for Flexible Robot Toward Transoral Procedures

Design and Verification of Parallelogram Mechanism With Geared Unit Rolling Joints for Reliable Wiring

The structure of 1-DOF joints used in existing robots is generally a revolute or a prismatic joint. However, recently, attempts have been made to apply rolling joints to reduce the size and weight of surgical and humanoid robots. In this study, to take advantages of wire routing through robot joints, a new method for applying geared rolling units to a parallelogram mechanism is proposed. First, a kinematic analysis of the proposed gear-based mechanism is explained in comparison with the existing pivot-based mechanism. In addition, the importance of the radii of the gears is verified through force analysis to prevent damage to the applied gears, as well as through the analysis of actuation torque and singular positions, in which the parallelogram can convert into an antiparallelogram. The effect of stable wiring was verified through an experiment using a cable-driven prototype. Consequently, the proposed parallelogram mechanism composed of rolling units is expected to be applied to various robot configurations owing to its advantages.