Vibration Of Arm Research Articles

Research on the influence of rigid body modes on the operating vibration of arc gate

Abstract The 5# arc working gate of Jiangshan Wanyao Reservoir is composed of the suspension system of the gate and the steel wire rope, which has a serious vibration phenomenon when running without water. Firstly, the rigid body modal analysis of the gate suspension system is analyzed, the position size of key components such as gate support hinge shaft, gate motion guide embedded parts, and main beam position state is measured and evaluated on site, and the dynamic stress and vibration of the support arm are tested and analyzed during gate operation. It is concluded that the influence rule and weight of the steel wire rope on the rigid body mode of the gate, the torsional position of the gate, and the uneven operation condition of the side guide lead to the rigid body mode of the gate. It is suggested to improve the twisting state of the gate, adjust the unevenness of the embedded parts, and weaken the factors that induce the modal vibration of the rigid body.

Modeling and Rotation Control Strategy for Space Planar Flexible Robotic Arm Based on Fuzzy Adjustment and Disturbance Observer

In precise space operation tasks, the impact of disturbing torques on the space flexible robotic arm (SFRA) cannot be ignored. Besides, the slender structure of the SFRA is very likely to generate vibration of the robotic arm. These are all potential hidden dangers in space safety. To quantify the potential risk, an accurate dynamics model of the SFRA considering the disturbing torque is built by Lagrange principle and the assumed modal method (AMM). Moreover, the effects of the disturbing torque, modal order and nonlinear terms on the deformation accuracy of the SFRA are compared. It is observed that the simplified dynamics model with neglecting the nonlinear terms (NNTs) has a high model accuracy and be easily solved. Therefore, the NNTs simplified model is chosen for deriving the transfer function of the SFRA. The parameters of the PI controller are adjusted in real time based on fuzzy rules to reduce the tracking error in the SFRA. In addition, the disturbance observer is designed to observe and compensate of the disturbance torque in the SFRA. The control method of adjusting controller parameters with fuzzy rules based on the disturbance observer greatly improves the rotational control accuracy of the SFRA. Finally, the validity of aforementioned control strategy is confirmed by simulation analysis and experimental results.

Research on vibration suppression of rigid flexible coupling manipulators based on genetic algorithm optimization

Aiming at the problem that the rigid flexible coupling manipulator generates elastic vibration during movement, which reduces the positioning accuracy and work efficiency, we propose a method of end vibration suppression based on cosine function superposition and multi population genetic algorithm. First, we get the relationship between the elastic vibration of the flexible arm and the joint trajectory motion according to the dynamic model of the system. Then, the cosine function superposition is used as the basis function to construct motion parameters of joints and the minimum residual vibration amplitude at the end of the flexible arm is used as the objective function. The undetermined coefficients in the basis function are optimized by multi population genetic algorithm to obtain the optimal trajectory. Finally, the simulation and experiment results show that the residual vibration amplitude is reduced by 60.6%. The proposed method can suppress the residual vibration at the end of the flexible arm and improve the work efficiency.

Nonlinear Vibration Control Experimental System Design of a Flexible Arm Using Interactive Actuations from Shape Memory Alloy.

The flexible arm easily vibrates due to its thin structural characteristics, which affect the operation accuracy, so reducing the vibration of the flexible arm is a significant issue. Smart materials are very widely used in the research topic of vibration suppression. Considering the hysteresis characteristic of the smart materials, based on previous simulation research, this paper proposes an experimental system design of nonlinear vibration control by using the interactive actuation from shape memory alloy (SMA) for a flexible arm. The experiment system was an interactive actuator-sensor-controller combination. The vibration suppression strategy was integrated with an operator-based vibration controller, a designed integral compensator and the designed n-times feedback loop. In detail, a nonlinear vibration controller based on operator theory was designed to guarantee the robust stability of the flexible arm. An integral compensator based on an estimation mechanism was designed to optimally reduce the displacement of the flexible arm. Obtaining the desired tracking performance of the flexible arm was a further step, by increasing the n-times feedback loop. From the three experimental cases, when the vibration controller was integrated with the designed integral compensator, the vibration displacement of the flexible arm was much reduced compared to that without the integral compensator. Increasing the number of n-times feedback loops improves the tracking performance. The desired vibration control performance can be satisfied when n tends to infinity. The conventional PD controller stabilizes the vibration displacement after the 7th vibration waveform, while the vibration displacement approaches zero after the 4th vibration waveform using the proposed vibration control method, which is proved to be faster and more effective in controlling the flexible arm's vibration. The experimental cases verify the effectiveness of the proposed interactive actuation vibration control approach. It is observed from the experimental results that the vibration displacement of the flexible arm becomes almost zero within less time and with lower input power, compared with a traditional controller.

Vibration and Trajectory Tracking Control of Engineering Mechanical Arm Based on Neural Network.

We offer a neural network-based control method to control the vibration of the engineering mechanical arm and the trajectory in order to solve the problem of large errors in tracking the path when the engineering mechanical arm is unstable and under the influence of the outside world. A mechanical arm network is used to perform tasks related to learning the unknown dynamic properties of a engineering mechanical arms keyboard without the need for prior learning. Given the dynamic equations of the engineering mechanical arm, the dynamic properties of the mechanical arm were studied using a positive feedback network. The adaptive neural network management system was developed, and the stability and integrity of the closed-loop system were proved by Lyapunov's function. Engineering mechanical arm motion trajectory control errors were modeled and validated in the Matlab/Simulink environment. The simulation results show that the management of the adaptive neural network is able to better control the desired path of the engineering mechanical arm in the presence of external interference, and the fluctuation range of input torque is small. The PID control has a large error in the expected trajectory tracking of the engineering mechanical arm, the fluctuation range of the input torque is as high as 20, and the jitter phenomenon is more serious. The use of detailed comparisons and adaptive neural network monitoring can perform well in manipulating the trajectory of the engineering mechanical arm. The engineering mechanical arm uses an adaptive neural network control method, in which the control precision of engineering mechanical arm motion trajectory can be improved and the out-of-control phenomenon of mechanical arm motion can be reduced.

A multi-objective optimization design of industrial robot arms

This paper introduces a multi-objective design mechanism to minimize both the initial and running costs of industrial robot arms. The goal of the design problem is to decide the type of material and physical dimensions of the robot arm to withstand high loads at vulnerable locations using stress analysis. Additionally, it selects the material architecture for the robot links based on a vibration analysis to avoid robot failure at or close to the resonance frequency. Hence, a set of design equations based on stress analysis are developed using analytical approaches while the findings are supported by finite element simulations in ANSYS. These decide the type of material, cross-section area, factor of safety (FoS), and maximum deflection of the robot links in terms of the mass-loads. Moreover, the vibration analysis is conducted to enhance the dynamic characteristics of the robot arm. Therefore, the excitation frequency is modified by changing the mass and the robot segment-material to evade working at the natural frequency. Modal analysis is conducted using ANSYS to identify the fundamental frequencies and their modal shapes. Then, a material selection mechanism based on finite element analysis is considered to allow a safe frequency operation range for the robot arm. A customized robot arm structure that combines Magnesium and Aluminum alloy with highly improved FoS and minimizes the initial and operating costs is proposed. In addition to the body structure of the robot arm, the influence of the reducers and motors on the stiffness and vibration of the robot arm is presented. Finally, the motion of the robot arm is optimized using a Genetic Algorithm subject to a set of boundary conditions imposed by the desired mission. The effect of rotation angle value in the power consumption is presented. The coefficients of a developed angular displacement function are optimized to ensure minimum power consumption during the robot missions.

Application of Three-Dimensional Animation in Mechanical Control Mechanism

With the development of the times and the advancement of science and technology, the development of 3D animation has gradually been applied in various fields. In the field of mechanical control, three-dimensional animation has gradually become a very important application. In the actual application process, the use of three-dimensional animation effects cannot be applied in the field of mechanical control only by imagination. It must be applied in practice from the perspective of mechanical control. Analyze from its own stability and external factors to realize its application value. The purpose of this paper is to study the application of 3D animation in mechanical control mechanism. This article will take mechanical control as an entry point to discuss the application of three-dimensional animation in its mechanism. The research is carried out from two aspects. The first is the application of the robot arm. Based on the kinematic path planning of the shortest time priority strategy, the shorter the motion time of the robot arm, the faster the speed, and the vibration is more difficult to avoid. This is the vibration of the flexible arm. Improve its work efficiency, lay the foundation for more complex path planning problems; create conditions for lighter and faster robotic arm applications. The second is the application of the mechanical foot. The proposed ankle joint control strategy based on the lateral and forward cycle matching can be combined with the forward plane walking control strategy under the stable initial gait of the robot to realize the humanlike virtual prototype of the biped robot. Dynamic walking for analysis. Experimental investigations have shown that in the process of normal walking, there is a dynamic swing process and a static support process. The swing process refers to the lifting of the foot to move forward or backward, and the supporting process refers to the immobilization of one foot to the other. One fulcrum on each foot allows it to move forwards and backwards. Among them, the dynamic swing process accounts for 40% of the whole process, and the static support process accounts for 60%. In general, based on these data, the three-dimensional robotic arm and three-dimensional robotic foot can be better studied.

Approximate Inertial Manifold-Based Model Reduction and Vibration Suppression for Rigid-Flexible Mechanical Arms

The dynamic characteristics of the mechanical arm with a rigid-flexible structure are very complex. The reason is that it is a complex DPS (distributed parameter system) with infinite dimension and nonlinearity in essence due to the rigid-flexible coupling. So, accurately positioning and controlling the rigid-flexible mechanical arms could be difficult. Therefore, a model reduction method of rigid-flexible mechanical arms based on the approximate inertial manifold is put forward. To repress the residual vibration of the end of the mechanical arm, a feedforward control strategy is designed. The high-dimensional solution of the vibration equation of the rigid-flexible mechanical arms is projected into the complete space composed of orthogonal decomposition modes. By using Galerkin’s method, the system is simplified and the approximate solution is obtained through the interaction between high-order and low-order modes. The truncated finite mode is also used to construct a lowest-order dynamic model on the basis of approximate inertia manifold. Given the reduced-order rigid-flexible mechanical arms dynamic model, dynamic response analysis is conducted to optimize the target position error and end residual vibration. A limited number of sinusoidal signals approximately combine the input signal, by using the particle swarm optimization algorithm to optimize the input signal, and the amplitude of the sinusoidal signal is corrected. The simulation results depict the superiority of the proposed method, which greatly suppresses the end residual vibration of the mechanical arm and realizes the accurate positioning of the end of the mechanical arm. In addition, the hardware experimental device of the rigid-flexible mechanical arms is constructed, and the experimental verification of the above method is put into effect. The simulation results of angular displacement and end vibration of the reduced model are accordant which is shown by the experimental results of the hardware platform.

Studying the wind-induced vibrations of a traffic signal structure through long term health monitoring

Recent failures of traffic signal structures have showcased the vulnerability of such structures to wind loading. During the wind-induced vibration of the mast arm, the large mass of the mast arm creates high-level stress at the pole-to-arm connection. Additionally the low mechanical damping results in accumulationof stress cycles ewhich could cause fatigue damage at the pole-to-arm connection. In this study, a traffic signal structure with three vertical traffic lights was selected for long-term health monitoring. The monitored acceleration data at the mast arm tip was used to study the wind-induced behavior and was compared with the theoretical analysis results. The monitored strain data at the pole-to-arm connection was used to evaluate the fatigue damage. Low stress ranges were recorded most of the time, which indicates that the wind-induced fatigue damage might not be a significant concern for the monitored traffic signal structure. However, high stress ranges have been recorded at high wind speeds, indicating fatigue damage can still be an issue at higher wind speed regions. The performance of monitored traffic signal structure was compared with those in the literature. An apparent discrepancy was noticed between their wind-induced behaviors, and the orientation of the attached traffic lights was identified as a key parameter to influence the wind-induced behavior. It was found that at low wind speed, attached vertical traffic lights can reduce the likelihood of vortex-induced vibration and, as a result, lower the stress range at the pole-to-arm connection.

Resonance Suppression Strategy for Humanoid Robot Arm

To address the problem of resonance in the control of a robot arm, a resonance suppression strategy is proposed for a single-joint humanoid robot arm based on the proportional-resonant(PR) controller. First, an arm joint model of the humanoid robot is established. Then the influence of resonance frequency on the performance of the control system with the robot arm is analyzed. The voltage fluctuation of the drive motor caused by the changes in arm motion is recognized as the disturbance of the current loop. The PR controller has the characteristic of disturbance rejection at a specific frequency. The output fluctuation of the driving system caused by the change of arm motion state at the resonance frequency is suppressed. Therefore the output current of the inverter will not be affected by the vibration of the arm at the resonance frequency. Finally, the control system is verified by MATLAB/Simulink simulation. The simulation results demonstrate that the control strategy for the humanoid robot arm based on the PR controller can suppress the resonance of the arm effectively, improving the dynamic performance and system stability.

Research on optimized time-synchronous online trajectory generation method for a robot arm

Based on sensor input, a robot arm should dynamically adjust its trajectory while maintaining stability to react to a sudden change in the target point in an unknown environment. To solve this problem, in this study, a time-optimized online trajectory generation (OTG) method is proposed using an S-curve velocity profile, which can generate trajectories in response to external sensor signals. The generated trajectory has characteristics that can guarantee the synchronization of multijoints according to an arbitrary initial state and a desired target state under velocity, acceleration, and jerk constraints. For multijoints time synchronization, two different characteristics are considered according to different application scenarios: minimum velocity or peak acceleration, which correspond to two sub-methods. The first one can be used to calculate with a minimum velocity peak, which can quickly adjust the trajectory according to the signal feedback. The second can be used to calculate the minimization of the acceleration peak, which can reduce the vibration of the robot arm due to a change in the motion. Compared with other OTG methods, the second proposed sub-method can effectively reduce the acceleration peak of the planned motion with the same synchronization time and parameters. Additionally, both sub-methods have the advantage of a rapid calculation and can generate time synchronization motion trajectories for 6 axes in 0.21 ms on a personal computer, fully satisfying the requirements of online motion planning. Finally, the effectiveness of the algorithm is verified by simulations and experiments with a lab-developed robot arm.

Method for suppressing residual vibration of robot arm through a heuristic algorithm

Method for suppressing residual vibration of robot arm through a heuristic algorithm

High-efficiency modal analysis and deformation prediction of rice transplanter based on effective independent method

The vibration problem associated with rice transplanters not only affects the quality and effect of the transplanting operation but also reduces the service life of the machine. With a focus on the vibration problem in the working process of a high-speed rice transplanter, a mechanical deformation prediction system based on the effective independence method for modal analysis was developed. This system simulates the vibration of the support arm of the transplanter during the working process of agricultural machinery. The deformation is predicted. With the use of the effective independence method, the measuring points that contribute the most to the target modal vector independence can be screened and retained as much as possible. In this way, there is greater assurance of more modal information being obtained under the limited sensor. Accuracy and mode requirements for experimental data were identified. In this paper, the experimental mode adopts the effective homology method to select the best measuring point and uses the pulse excitation method to collect data and analyze and calculate the DH5902 dynamic signal acquisition and analysis system to obtain the natural frequency and vibration mode of the support arm. Based on this, the SolidWorks software is used to model the key components of the transplanter power transmission system. The model is imported into ANSYS Workbench and combined with the Lanczos Method solution to solve the natural frequency and vibration mode. The accuracy of this modal test analysis method was verified. The results show that the first-order natural frequency of the transplanter is 102.68 Hz, which is within the excitation frequency range of the engine (86.67–120 Hz). Therefore, when the rice transplanter is working at high speed, the engine and the support arm will resonate, thus impacting the seedlings and machinery. The service life is also impacted. The research results provide a theoretical basis for the deformation prediction during the use of the support arm of the transplanter and provide a reference for the vibration-damping optimization design of the support arm structure and size of the subsequent transplanter.

Research on vibration suppression mode of sorting arm structure in high-frequency reciprocating motion

The sorting arm structure is under the inertia impact of high frequency reciprocating motion. The vibration characteristics are related to the operation process so that the precision of the chip sorting is uncertain. Thus, the accuracy of chips and efficiency of LED sorting machine are reduced. In the paper, the relationship between the vibration of the sorting arm and the positioning error of the chip has been studied. Besides, the correlation between the sorting arm structure’s vibration and the working precision of the separator are pointed out. The operation control is optimized based on the dynamics of the sorting arm and the operation parameters are optimized based on time sequence setting, in order to shorten the vibration attenuation time of the sorting arm for suppress vibration and provide efficiency. The incentives, which are introduced by variable structure and by the operation, can be effectively controlled. The array accuracy of chips and working efficiency of chip sorting machine are improved.

Analysis of vibration of pendulum arm under bursting oscillation excitation

We investigate numerically the responses of the single pendulum and double pendulum arms coupled to a nonlinear RLC-circuit shaker through a magnetic field. These systems can be used to build a robotic device or an automat. The nonlinear RLC circuit is a Duffing oscillator that generates electric bursting oscillations. We first examine the dynamical behaviour of the single pendulum arm. Time series shows that the pendulum arm exhibits bursting oscillation. When the natural frequency $$w_2 <1$$ , the shape of the bursting in the electrical part is different from that observed in the pendulum arm and if $$w_2 >1$$ , the shape is the same. We then explore the behaviour of a double pendulum arm powered by electric bursting oscillations. Time series are also used to explore the behaviour of each pendulum arm. The results show that the displacement of each pendulum arm undergoes bursting oscillations resulting from the transfer of the electronic signal. The shape of bursting of the first pendulum is different from that of the second pendulum for some values of $$w_1 $$ . The shape, period and amplitude of the bursting oscillations depend on various control parameters.

An Operator-based Nonlinear Vibration Control System Using a Flexible Arm with Shape Memory Alloy

In the past, arms used in the fields of industry and robotics have been designed not to vibrate by increasing their mass and stiffness. The weight of arms has tended to be reduced to improve speed of operation, and decrease the cost of their production. Since the weight saving makes the arms lose their stiffness and therefore vibrate more easily, the vibration suppression control is needed for realizing the above purpose. Incidentally, the use of various smart materials in actuators has grown. In particular, a shape memory alloy (SMA) is applied widely and has several advantages: light weight, large displacement by temperature change, and large force to mass ratio. However, the SMA actuators possess hysteresis nonlinearity between their own temperature and displacement obtained by the temperature. The hysteretic behavior of the SMA actuators affects their control performance. In previous research, an operator-based control system including a hysteresis compensator has been proposed. The vibration of a flexible arm is dealt with as the controlled object; one end of the arm is clamped and the other end is free. The effectiveness of the hysteresis compensator has been confirmed by simulations and experiments. Nevertheless, the feedback signal of the previous designed system has increased exponentially. It is difficult to use the system in the long-term because of the phenomenon. Additionally, the SMA actuator generates and radiates heat because electric current passing through the SMA actuator provides heat, and strain on the SMA actuator is generated. With long-time use of the SMA actuator, the environmental temperature around the SMA actuator varies through radiation of the heat. There exists a risk that the ambient temperature change dealt with as disturbance affects the temperature and strain of the SMA actuator. In this research, a design method of the operator-based control system is proposed considering the long-term use of the system. In the method, the hysteresis characteristics of the SMA actuator and the temperature change around the actuator are considered. The effectiveness of the proposed method is verified by simulations and experiments.

Research on dynamics of sorting arms with high frequency reciprocating motion

The characters of high frequency reciprocating equipment are quick starting and stopping, short range, high frequency and multi-freedom reciprocating motion. The inertia introduced by the high frequency reciprocating motion of a LED chip sorter has complicated effects on the positional accuracy. It is necessary to obtain dynamics of the sorting arm to suppress the vibration of the high frequency operation. The positioning precision and positioning time are affected by the natural vibration of the sorting arm by analyzing the displacement response. The paper verifies that the inherent vibration of the sorting arm has a crucial effect on its positioning precision and positioning time. Under static condition, due to the additional mass of the accelerometers, the research results show that there is no obvious difference in the experimental modal analysis (EMA) based on multi-type sensors. The modal parameters identified by accelerometers and strain gauges are very close. The modal parameters are obtained through the modal analysis method, which combines the strain modal analysis and operational modal analysis (OMA), under high frequency reciprocating motion. The paper verifies that the modal parameters of lightweight structure are very different in the static and operation. The key points of each mode are found by analyzing the modal amplitudes at different speeds which provide the guiding principle and basis for the dynamic optimization of the sorting arm mechanism.

Vibration Reduction for a Flexible Arm Using Magnetorheological Elastomer Vibration Absorber

The application of the magnetorheological elastomer (MRE) to nonlinear vibration control for a flexible arm is investigated in this paper. A semiactive control method is suggested to reduce vibration via the internal resonance and the MRE. To establish a vibration energy transfer channel, a tuned vibration absorber based on the MRE is developed. Through adjusting the coil current, the frequency of the vibration absorber can be readily controlled by the external magnetic field, thereby maintaining the internal resonance condition with the flexible arm. By the perturbation analysis, it is proven that the internal resonance can be successfully established between the flexible arm and the MRE vibration absorber, and the vibration energy of the flexible arm can be transferred to and dissipated by the MRE vibration absorber. Through numerical simulations, virtual prototyping simulations, and experimental investigation, it is verified that the proposed method and the suggested MRE vibration absorber are effective in controlling nonlinear vibration of the flexible arm.

Derivation of dynamic equation of viscoelastic manipulator with revolute–prismatic joint using recursive Gibbs–Appell formulation

In this paper, the motion analysis of a viscoelastic manipulator with N-flexible revolute–prismatic joints is being studied with the help of a systematic algorithm. The presence of prismatic joints, along with revolute ones, makes the derivation of the equations complicated. The link’s axial motions cause variation of its flexible parts with respect to time. In order to modify the associated mode shapes concerning an instant link length, dynamic interaction between the rotary reciprocating motion and transverse vibration of the flexible arm is evaluated. The links are modeled on the assumed mode method using the Timoshenko beam theory (TBT). Dynamic equations are derived from the recursive Gibbs–Appell formulation. The formulation involves fewer mathematical calculations but shows efficient computational performance when compared to other formulations. The dynamic model of each joint shows flexibility, damping, backlash and frictions resulting in accuracy of the formulations. Applying recursive algorithm based on the $$3\times 3$$ rotational matrix instead of the $$4\times 4$$ one causes the computational performance to fall by separating the rotating matrix. Furthermore, motion equations are obtained symbolically and systematically. Links linear motion causes TBT mode shapes changes with respect to time. This is implemented in a non-dimensional form to avoid computing for each step. Finally, the following dynamic equations are solved numerically by MATLAB software for a spatial two-armed manipulator. The outcome of the simulations represents the ability of the proposed algorithm to derive and solve the equations of motion. Moreover, the data are compared with the rigid and elastic links, modeled by the Euler–Bernoulli beam theory.

Real-Time and Noncontact Impulse Radio Radar System for $\mu \text{m}$ Movement Accuracy and Vital-Sign Monitoring Applications

In this paper, a real-time, contactless pulse-based ultra-wideband (UWB) radar sensor was used to precisely detect the movement of the robotic arm, heartbeats, and respiration activities. To increase the object tracking resolution, an algorithm using adaptive and digitalized post-calibration techniques were proposed and tested. Both the radiated and reflected analog pulses were converted to digital signals by a low-noise comparator and its buffer for the time interval and distance detection. Moreover, the dynamic and calibrated tracking mechanism was incorporated into the algorithm for improving tracking accuracy and to continuously localize an object’s vibration. The measured performance revealed that the proposed method successfully achieved $\mu \text{m}$ movement precision, thus providing its excellent tracking ability. We performed three different experimental tests to demonstrate the UWB radar’s viability. First, the radar was employed to detect the undesired structural vibration of a delta robotic arm, which was subjected to high acceleration and structural flexibility. The measured results indicated that the accuracy of $100~\mu \text{m}$ can be achieved at a 10 Hz vibration frequency. Next, the apnea alarm was tested, which included an embedded sensitive sensor in the smart mattress in order to execute long-term physiological monitoring. The apnea was mitigated by auto-adjusting the patient’s sleeping posture on the mattress when the UWB sensor detected the apnea condition. The final experiment using the radar sensor was to monitor human vital signs, such as heart and breathing rates, simultaneously. In comparison with a commercial electrocardiography instrument, this radar sensor measured 73.2 bpm with only 1.2% deviation. Our results shown that the contactless UWB sensor performs superbly and is well-suited for monitoring physiological parameters.