Double Parallelogram Mechanism Research Articles

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.

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.

CURER: A Lightweight Cable-Driven Compliant Upper Limb Rehabilitation Exoskeleton Robot

Upper limb exoskeletons show promise for improving functionalities required for stroke patients. Despite recent progress, most of current upper limb rehabilitation devices are still bulky, heavy, and less compliant to be applied. This article presents a cable-driven compliant upper limb rehabilitation exoskeleton robot (CURER) with a lightweight frame and comfortable human–robot interaction. A modular series elastic actuator (SEA) was designed to provide controlled torque for each active robotic joint, and Bowden cables were applied to transfer controlled torque to distal joints. A six-bar double parallelogram mechanism was designed to implement 3 active degrees of freedom (DOFs) of a shoulder. An actuated elbow with 1 DOF and a wrist with a passive DOF were also developed for CURER. The anthropomorphic shoulder, elbow, and wrist joints can minimize misalignment between human upper limbs and the robot. The length of anthropomorphic arm was adjustable for a wide range of users. It can apply up to a 33 N·m torque in shoulder flexion/extension, abduction/adduction, intra/extra rotation, and elbow flexion/extension, with a range of 7.6–8.0 Hz position bandwidth in each actuation. CURER has a large range of motion and can provide accurate torque control for stroke patients’ requirements. Besides, a comprehensive rehabilitation strategy including robot-in-charge mode and human-in-charge mode was developed for different recovery stages. Experiments carried out on CURER actuation units demonstrated good position and impedance control performance. Finally, a virtual reality training system was developed to assist the subjects to accomplish upper limb rehabilitation efficiently.

Design of a transrectal ultrasonic guided prostate low dose rate brachytherapy robot

Abstract. Transrectal prostate brachytherapy (BT) can effectively treat prostate cancer. During the operation, doctors need to hold the ultrasound probe for repeated adjustments, which makes it difficult to ensure the efficiency, accuracy, and safety of the operation. We designed an 11 DOF (degrees of freedom) active and passive transrectal BT robot, based on the analysis of the transrectal prostate BT process. The posture adjustment module designed, based on the double parallelogram mechanism, realizes the centering function of the ultrasound probe and performs the kinematic analysis. Based on Simscape Multibody, the working posture and centering effect of the ultrasound probe's different feed distances are simulated. A physical prototype of the transrectal BT robot was developed and measured in experiments. The experimental results indicate that the angle rotation error of the joint is controlled to within 1∘. The rotation range of each joint meets the design requirements. The maximum error of the yaw angle's remote center point motion and pitch angle's remote center point motion are 0.5 and 0.4 mm, respectively, which are less than the deformation that can be endured in the anus by 6 mm. The simulation and experimental results and the analysis of measurement errors have verified the effectiveness and stability of the transrectal BT robot.

Real time motion intention recognition method with limited number of surface electromyography sensors for A 7-DOF hand/wrist rehabilitation exoskeleton

The functions of human hand are rich, and the motor dysfunction of hand of chronic stroke patients can be alleviated to some extent through active rehabilitation training. Hand rehabilitation exoskeleton can assist patients to do active rehabilitation training. However, how to realize more motion with less surface electromyogrphy (sEMG) sensors, and how to realize the real-time motion intention recognition are two important issues. This paper introduces real-time motion intention recognition method with limited number of sEMG sensors for a 7-DOF wearable hand/wrist rehabilitation exoskeleton to realize the real-time motion intention recognition and rehabilitation training. Root mean square (RMS) and Bens Spiker Algorithm (BSA) features of three-channel sEMG signals are extracted, and they are mapped to seven different intention movements by combining the Bagging method. The finger structure part of the exoskeleton is composed of a rotary-spatial-spatial-rotary (RSSR) mechanism and a double-parallelogram mechanism, which makes the projection center of exoskeleton coincide with the rotation center of the hand joint. The average real-time motion intention recognition accuracy is 95.37 ± 0.97%.

Modeling and analysing of spring-loaded double parallelogram mechanism using moment balance

Double Parallelogram Lifting Mechanism (DPLM) is a multi-linkage mechanism adopted as the lifting mechanism of the designed robot in this paper. DPLM is designed based on Double Parallelogram Mechanism (DPM), making it a compact and stable multi-linkage mechanism with a low retracted height and a great working height. This paper investigates the condition in which DPLM obtains static equilibrium at any height using Hookean springs and the minimization of the motor’s required torque exertion against the gravitational moment of the weight of the mechanism. A mathematical model describing all the factors involved in moment balancing of DPLM is derived and established in MATLAB and is verified through experiments with a virtual prototype conducted in SOLIDWORKS. The obtained results show that the magnitude of the moment exerted by the tension of a spring can be determined not only by its exact installation positions but also by its D value, which is the difference in the distances between the two installation points of a spring and their respective rotation axes. An optimization method based on minimizing the RMSE of the unbalanced moment for DPLM is introduced.

Paired double parallelogram flexure mechanism clamped by corrugated beam for underconstraint elimination.

This Note presents a kind of paired double parallelogram (DP) flexure mechanism clamped by a sinusoidal corrugated beam to solve the problem of underconstraint of its secondary stages. The results show that the proposed mechanism effectively constrains the undesired motions of the secondary stages without changing the stiffness and the first-order natural frequency in the working direction. The second- and third-order natural frequencies of the mechanism are increased by 9.2% and 30.8%, respectively, which can effectively improve the dynamic characteristics of the DP mechanism.

Dimensional Optimization for Minimally Invasive Surgery Robot Based on Double Space and Kinematic Accuracy Reliability Index

Abstract To improve the kinematic performance of the remote center mechanism for surgical robot, a double space index and kinematic accuracy reliability index are proposed to optimize the dimensional sizes of mechanism. First, the influence of the angular error on the position error and the operability of the remote center in the workspace are analyzed. The position error space and operability space index are weighted to establish the double space index. Second, a kinematic accuracy reliability index is established based on the influence of joint clearance on output position accuracy. Finally, the dimensional sizes of remote center adjustment mechanism and double parallelogram mechanism are optimized based on proposed optimization indices. Multipopulation genetic algorithm is used to obtain the optimal size parameters under the corresponding index. The optimized double space index is 56.7%, which is 56.5% higher than before optimization. The optimized kinematic accuracy reliability is 0.91, which is 22.9% higher than before optimization. The kinematic performance of remote center mechanism has been significantly improved after optimization.

An Efficient Parking Solution: A Cam-Linkage Double-Parallelogram Mechanism Based 1-Degrees of Freedom Stack Parking System

To solve the difficult parking problem, developing a mechanical parking device is a practical approach. Aiming at longitudinal parking, a novel compact double-stack parking system is put forward based on a 1-DOF (degree of freedom) cam-linkage double-parallelogram mechanism. Due to the unique structure, the whole device can be driven by a single motor to realize three motion periods, including lifting, translation, and fillet transition. Meanwhile, all parts of this compact mechanism can be well contained in the filleted rectangular trajectory. This rectangular trajectory is essential that we no longer need to take out the ground vehicles so as to realize stack parking. Furthermore, to overcome the singularity collinear problem of the parallelogram which may lead to the polymorphic state, the double-parallelogram mechanism is proposed to maintain the orientation of the parking platform. The digital simulation and kinetostatic analysis results demonstrate the feasibility that this novel cam-linkage double-parallelogram mechanism can improve the space utilization of the residential area, alleviate the parking problem, and can be quickly put into application on campuses or streets in a short period.

High resolution flexible 4-PPR U-base planar parallel microstage robotic manipulator

Numerous compliant manipulators, actuated by voice coil, have been developed and are widely used for micro/nano-manipulation. One of the greatest difficulties lies in optimizing the design with consideration of various parameters like high stiffness, large amplification, higher precise tracking, and highly accurate positioning. A modular and compact planar 3PPR+PPR parallel micro positioning platform is presented (3-degrees of freedom) and its symmetric design equips it with various advantages. The parallel-kinematic arrangement of the manipulator with optimum sizes results in high rigidity and greater load carrying capacities. The proposed planar parallel compliant manipulator possesses higher structural rigidity, better amplification, higher accuracy and precision trajectory tracking ability and positioning. The present work is on a flexure-based micro positioning stage with 3 degrees-of-freedom, incorporating compliant double parallelogram mechanism. An innovative idea of multistage compliant compound parallelogram mechanism is proposed here for the development of a three degrees-of-freedom (X-Y- θ) micro-positioning system, with the range of motion larger than 10 mm. The established models and the performance of the proposed stage are verified through finite-element analysis (FEA).

S-Surge: Novel Portable Surgical Robot with Multiaxis Force-Sensing Capability for Minimally Invasive Surgery

To achieve a compact and lightweight surgical robot with force-sensing capability, in this paper, we propose a surgical robot called “S-surge,” which is developed for robot-assisted minimally invasive surgery, focusing mainly on its mechanical design and force-sensing system. The robot consists of a 4-degree-of-freedom (DOF) surgical instrument and a 3-DOF remote center-of-motion manipulator. The manipulator is designed by adopting a double-parallelogram mechanism and spherical parallel mechanism to provide advantages such as compactness, simplicity, improved accuracy, and high stiffness. Kinematic analysis was performed in order to optimize workspace. The surgical instrument enables multiaxis force sensing including a three-axis pulling force and single-axis grasping force. In this study, it will be verified that it is feasible to carry the entire robot around thanks to its light weight (4.7 kg); therefore, allowing the robot to be applicable for telesurgery in remote areas. Finally, it will be explained how we experimented with the performance of the robot and conducted tissue manipulating task using the motion and force sensing capability of the robot in a simulated surgical setting.

Al-Zahrawi: A Telesurgical Robotic System for Minimal Invasive Surgery

Surgical robots provide various advantages, such as improved precision and dexterity, over conventional surgical procedures and have been extensively studied in the last decade. Many surgical robots have been recently developed and described in the literature. However, given their multidisciplinary nature, due to the involvement of medical surgery, electrical engineering, mechanical engineering, and computer science, very few existing documents provide a system design perspective of a complete surgical robot. We tend to fill this gap by presenting the complete system-level design of Al-Zahrawi, which is a new telesurgical robotic system. The Al-Zahrawi system is mainly composed of two parts, i.e., a master console and a slave console, which are connected through a communication link. The master console consists of master manipulators (MMs), visual information presentation apparatus, and foot pedals. The slave console is primarily composed of three slave manipulators (SMs): The left and right manipulators are equipped with surgical instruments, whereas the middle one holds the endoscope. All the manipulators utilize the modified double parallelogram mechanism to achieve the remote center of motion. The distinguishing features of this system include: 1) a custom-made simple-in-construction user-friendly MMs; 2) a modular SM, with an interchangeable instrument module that does not contain any electronic circuitry and thus can be completely sterilized with ease; and 3) the availability of an independent forceps jaw movement, which increases the dexterity of the surgical tool tip without using the wrist mechanism.

Multiple-Degree-of-Freedom Counterbalance Robot Arm Based on Slider-Crank Mechanism and Bevel Gear Units

Low-cost but high-performance robot arms are required for robot arms to come into widespread use. To provide sufficient torques to support the robot mass and payload, most arms use expensive motors and speed reducers, which are the main reasons for their high price. As a solution to these problems, a multiple-degree-of-freedom (DOF) counterbalance mechanism and robot arm were developed in our previous study, which can compensate for the gravitational torque due to the robot mass. However, there are durability and reliability problems associated with wire-based mechanisms. To solve these, in this study, we proposed a new counterbalance mechanism based on a spring and slider-crank mechanism, along with a double-parallelogram mechanism composed of bevel gear units. Moreover, a 6-DOF counterbalance robot arm was built to verify the performance of the proposed mechanism. Simulation and experimental results showed that the proposed mechanism effectively decreased the torque required to support the robot mass, thus allowing the prospective use of low-cost motors and speed reducers for high-performance robots.

A large-range compliant micropositioning stage with remote-center-of-motion characteristic for parallel alignment

Micro-/nanopositioning stage with remote-center-of-motion (RCM) plays a key role in precision out-of-plane aligning since it can eliminate harmful lateral displacement generated at the output platform. This paper presents the design, modeling and test of a novel large-range flexure-based micropositioning stage with RCM characteristic. The stage is composed of an outer RCM guiding mechanism and a inner output-stiffness enhanced lever amplifier (OELA). The outer RCM guiding mechanism is constructed by a symmetric double parallelogram mechanism which can guide the stage to perform a RCM movement with high rotational precision. The inner OELA is designed to amplify the output displacement of the adopted piezoelectric stack actuator (PSA). Compared with conventional lever amplifier, the proposed OELA possesses twice the output stiffness, which makes it more appropriate for actuating the outer mechanism and therefore, a large rotational range can be obtained. Based on the pseudo-rigid-body-model (PRBM) method, the analytical models predicting kinematics, statics, and dynamics of the RCM stage have been established. Besides, the dimensional optimization is conducted in order to maximize the first resonance frequency of the stage. After that, finite element analysis is carried out to validate the established models and the prototype of the stage is fabricated for performance tests. The experimental results show that the developed RCM stage has a rotational range of 6.96 mrad while the maximum center shift of the RCM point is as low as $$9.2\,{\upmu } \text {m}$$9.2μm, which validate the effectiveness of the proposed scheme.

Multi-DOF Counterbalance Mechanism for a Service Robot Arm

Low-cost but high-performance robot arms are required for widespread use of service robots. Most robot arms use expensive motors and speed reducers to provide torques sufficient to support the robot mass and payload. If the gravitational torques due to the robot mass, which is usually much greater than the payload, can be compensated for by some means; the robot would need much smaller torques, which can be delivered by cheap actuator modules. To this end, we propose a novel counterbalance mechanism which can completely counterbalance the gravitational torques due to the robot mass. Since most 6-DOF robots have three pitch joints, which are subject to gravitational torques, we propose a 3-DOF counterbalance mechanism based on the double parallelogram mechanism, in which reference planes are provided to each joint for proper counterbalancing. A 5-DOF counterbalance robot arm was built to demonstrate the performance of the proposed mechanism. Simulation and experimental results showed that the proposed mechanism had effectively decreased the torque required to support the robot mass, thus allowing the prospective use of low-cost motors and speed reducers for high-performance robot arms.

Conceptual design of compliant translational joints for high-precision applications

Compliant translational joints (CTJs) have been extensively used in precision engineering and microelectromechanical systems (MEMS). There is an increasing need for designing higher-performance CTJs. This paper deals with the conceptual design of CTJs via three approaches: parallelogram based method, straight-line motion mechanism based method and combination based method. Typical emerging CTJ designs are reviewed by explaining their design principles and qualitatively analyzing their characteristics. New CTJs are proposed using three approaches, including an asymmetric double parallelogram mechanism with slaving mechanism, several compact and symmetric double parallelogram mechanisms with slaving mechanisms and a general CTJ using the center drift compensation and a CTJ using Roberts linkage and several combination designs. This paper provides an overview of the current advances/progresses of CTJ designs and lays the foundation for further optimization, quantitative analysis and characteristic comparisons.

A parallelogram-based compliant remote-center-of-motion stage for active parallel alignment.

Parallel alignment stage with remote-center-of-motion (RCM) is of key importance in precision out-of-plane aligning since it can eliminate the harmful lateral displacement generated at the output platform. This paper presents the development of a parallelogram-based compliant RCM stage for active parallel alignment. Different from conventional parallelogram-based RCM mechanism, the proposed stage is designed with compliant mechanisms, which endows the stage with many attractive merits when used in precision micro-/nanomanipulations. A symmetric double-parallelogram mechanism (SDPM) based on flexure hinges is developed as the rotary guiding component to realize desired RCM function. Due to the geometrical constraint of the SDPM, the operating space of the stage can be easily adjusted by bending the input links without loss of rotational precision. The stage is driven by a piezoelectric actuator and its output motion is measured by non-contact displacement sensors. Based on pseudo-rigid-body simplification method, the analytical models predicting kinematics, statics, and dynamics of the RCM stage have been established. Besides, the dimensional optimization is conducted in order to maximize the first resonance frequency of the stage. After that, finite element analysis is conducted to validate the established models and the prototype of the stage is fabricated for performance tests. The experimental results show that the developed RCM stage has a rotational range of 1.45 mrad while the maximum center shift of the RCM point is as low as 1 μm, which validate the effectiveness of the proposed scheme.

Conceptual design and dimensional synthesis of “MicroHand”

Abstract A master–slave surgical robotic system can make the best use of both a doctor’s experience and the characteristics of precise positioning, stable performance and dexterous manipulability of a robot. A new surgical robotic system “MicroHand” is presented in this paper with a master–slave isomerous mechanism to provide more design freedoms. The master of “MicroHand” is a Phantom Desktop device and the slave manipulator is a system designed using a position mechanism and an orientation mechanism. The position mechanism implements the kinematic characteristics of a double parallelogram mechanism driven by a cable, which can decouple the position and posture of the slave manipulator. The orientation mechanism applies three rotating axes intersecting at one point to ensure that the surgical tools have enough dexterity at any position in the workspace. The position mechanism and its parameters are designed based on kinematic analysis of two cable-driven linkage structures and kinematic conditioning index. The suitable positions are analyzed in the workspace of a single arm and also in the coworkspace of the two arms. The optimal results show that the “MicroHand” system can enhance the ability of the surgeon in a blood vessel (1 mm in diameter) suturing and knotting experiment.