Robot Arm Motion Research Articles

Iterative path-accurate trajectory generation for fast sensor-based motion of robot arms

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Posture Control Considering Joint Stiffness of a Robotic Arm Driven by Rubberless Artificial Muscle

This paper describes a joint angle control considering the passive joint stiffness of robotic arms driven by rubberless artificial muscle (RLAM), which is a pneumatic actuator. The contraction mechanism of RLAM is the same as that of the McKibben artificial muscle. Unlike the McKibben artificial muscle, RLAM is constructed using an airbag made of a nonelastic material instead of a rubber tube.The objective of this study is to realize a soft contact movement of robotic arms by applying the passive compliance characteristics of RLAMs. In this study, we derive a mathematical expression for the relationship between the output of an RLAM and the joint stiffness of a robotic arm. In addition, we suggest a control scheme for each RLAM. We confirm the validity of these suggestions experimentally. From the result, we observe a good control performance of the joint angle. A robotic arm moves smoothly according to the force added from outside by setting the passive stiffness of the arm.

Hybrid vibration and rest-to-rest control of a two-link flexible robotic arm using H∞ loop-shaping control design

Purpose This study presents a method for simultaneous motion and vibration control of light-weight slender robotic arms, known as flexible manipulators. In this paper, a new control algorithm is proposed for a two-link manipulator with elastic links. Design/methodology/approach The controller includes a MIMO H∞ Loop-Shaping Design (H∞LSD) as the feedback controller, and a command pre-shaping filter as the feed-forward controller. The conventional inputs and outputs of a typical two-link manipulator , that consists of the torques applied by the actuators at the joints, and the joint angles are chosen for the feedback control. Findings It is shown that by selecting a proper desired loop shape, the H∞LSD is able to control the joint angles of the manipulator, and simultaneously, suppress vibrations of the system so that the high frequency chatter due to the structural vibration modes does not appear at the outputs. Then it is shown that when the H∞LSD is equipped with a command pre-shaping filter, more efficient suppression of the chatter at the tip of the manipulator is achieved. The capability and effectiveness of the proposed control strategy in driving and stabilizing the manipulator to desired positions and simultaneously suppressing structural vibrations is shown by the simulation of the flexible manipulator in rest-to-rest maneuvers. Practical implications Flexible Manipulator, Space Manipulators Originality/value A robust MIMO controller is proposed for simultaneous motion and vibration control of flexible manipulator.

New Possibilities of Robot Arm Motion Simulation

The importance of computer simulations of the industrial robot arm motions at the technological scene becomes more important especially in connection with industrial applications of the new types of robot arm kinematic structures or with solving the human robot safety collaboration in industry. The article is aimed at the simulation of the basic (primitive) tasks executed by industrial robot with utilization of software packages of the "open-source" platform ROS. ROS is the software of modular architecture that extends the capabilities of the different robot types programming and controlling.

Adapting a Low-Cost Selective Compliant Articulated Robotic Arm for Spillage Avoidance

Flexible automation systems provide the needed adaptability to serve shorter-term projects and specialty applications in biochemical analysis. A low-cost selective compliant articulated robotic arm designed for liquid spillage avoidance is developed here. In the vertical-plane robotic arm movement test, the signals from an inertial measurement unit (IMU) and accelerometer were able to sense collisions. In the horizontal movement test, however, only the signals from the IMU enabled collision to be detected. Using a calculation method developed, it was possible to chart the regions where the obstacle was likely to be located when a collision occurred. The low cost of the IMU and its easy incorporation into the robotic arm offer the potential to meet the pressures of lowering operating costs, apply laboratory automation in resource-limited venues, and obviate human intervention in response to sudden disease outbreaks.

Robot-assisted automatic ultrasound calibration.

Ultrasound (US) calibration is the process of determining the unknown transformation from a coordinate frame such as the robot's tooltip to the US image frame and is a necessary task for any robotic or tracked US system. US calibration requires submillimeter-range accuracy for most applications, but it is a time-consuming and repetitive task. We provide a new framework for automatic US calibration with robot assistance and without the need for temporal calibration. US calibration based on active echo (AE) phantom was previously proposed, and its superiority over conventional cross-wire phantom-based calibration was shown. In this work, we use AE to guide the robotic arm motion through the process of data collection; we combine the capability of the AE point to localize itself in the frame of the US image with the automatic motion of the robotic arm to provide a framework for calibrating the arm to the US image automatically. We demonstrated the efficacy of the automated method compared to the manual method through experiments. To highlight the necessity of frequent ultrasound calibration, it is demonstrated that the calibration precision changed from 1.67 to 3.20mm if the data collection is not repeated after a dismounting/mounting of the probe holder. In a large data set experiment, similar reconstruction precision of automatic and manual data collection was observed, while the time was reduced by 58%. In addition, we compared ten automatic calibrations with ten manual ones, each performed in 15min, and showed that all the automatic ones could converge in the case of setting the initial matrix as identity, while this was not achieved by manual data sets. Given the same initial matrix, the repeatability of the automatic was [0.46, 0.34, 0.80, 0.47] versus [0.42, 0.51, 0.98, 1.15]mm in the manual case for the US image four corners. The submillimeter accuracy requirement of US calibration makes frequent data collections unavoidable. We proposed an automated calibration setup and showed feasibility by implementing it for a robot tooltip to US image calibration. The automated method showed a similar reconstruction precision as well as repeatability compared to the manual method, while the time consumed for data collection was reduced. The automatic method also reduces the burden of data collection for the user. Thus, the automated method can be a viable solution for applications that require frequent calibrations.

A New Artificial Neural Network Approach in Solving Inverse Kinematics of Robotic Arm (Denso VP6242).

This paper presents a novel inverse kinematics solution for robotic arm based on artificial neural network (ANN) architecture. The motion of robotic arm is controlled by the kinematics of ANN. A new artificial neural network approach for inverse kinematics is proposed. The novelty of the proposed ANN is the inclusion of the feedback of current joint angles configuration of robotic arm as well as the desired position and orientation in the input pattern of neural network, while the traditional ANN has only the desired position and orientation of the end effector in the input pattern of neural network. In this paper, a six DOF Denso robotic arm with a gripper is controlled by ANN. The comprehensive experimental results proved the applicability and the efficiency of the proposed approach in robotic motion control. The inclusion of current configuration of joint angles in ANN significantly increased the accuracy of ANN estimation of the joint angles output. The new controller design has advantages over the existing techniques for minimizing the position error in unconventional tasks and increasing the accuracy of ANN in estimation of robot's joint angles.

Gait Balance and Acceleration of a Biped Robot Based on Q-Learning

This paper presents a method for the biped dynamic walking and balance control using reinforcement learning, which learns dynamic walking without a priori knowledge about the dynamic model. The learning architecture developed is aimed to solve complex control problems in robotic actuation control by mapping the action space from a discretized domain to a continuous one. It employs the discrete actions to construct a policy for continuous action. The architecture allows for the scaling of the dimensionality of the state space and cardinality of the action set that represents new knowledge, or new requirements for a desired task. The balance learning method utilizing the motion of robot arm and leg to shift the zero moment point on the soles of a robot can maintain the biped robot in a static stable state. This balanced algorithm is applied to biped walking on a flat surface and a seesaw and is making the biped’s walks more stable. The simulation shows that the proposed method can allow the robot to learn to improve its behavior in terms of walking speed. Finally, the methods are implemented on a physical biped robot to demonstrate the feasibility and effectiveness of the proposed learning scheme.

Experimental Measurements of Near-Source Exposure Modeling Parameters

Air concentrations near pollutant sources can be modeled using two-zone and turbulent diffusion models. Each type of model requires a specific pollutant transport parameter: the interzonal air flow (β) is used in the two-zone model and the turbulent diffusion coefficient (DT) in the diffusion model. In this study β and DT were determined experimentally by using concentrations measured around the release of a tracer vapor. A robot arm provided motion in the space near the source to simulate worker actions. Eighty-two experiments were conducted at two room locations and with different robot arm motion programs. β and DT for were calculated using room geometry, ventilation parameters and the measured concentrations during the experiments. The near zone geometry was a 0.4 m hemisphere. The presence of motion in the vicinity of the source was important for the appropriate application of both models. The values of β were log-normally distributed with a mean of 2.03 m3/min, a geometric mean (GM) of 1.65 m3/min (1.42–1.93 95% C.I.) and a geometric standard deviation of 1.82. DT was also log-normally distributed with a mean of 0.586 m2/min, a GM of 0.545 m2/min (0.493–0.600 95% C.I.) and GSD of 1.45. The location within the room had an influence on the value of both β and DT. The use of random airspeed and the free surface area around the source was confirmed as an appropriate method for determining β. A recently developed algorithm was supported as useful for determination of DT. The results strengthen the application of both the two-zone and turbulent diffusion models for worker exposure modeling.

Intelligent humanoid mobile robot with embedded control and stereo visual feedback

Generally, an intelligent humanoid robot system should have dual arms, mobile ability and stereo vision for establishing the interactive capability in unknown environment. Stereo vision system detects unknown objects or obstacles from their visual range and estimates 3D coordinates in a working environment. Dual arms and mobile platform are employed to approach the detected object and execute interaction based on visual servo information. Here a wheel-based 10 DOF dual arms mobile robot with FPGA hardware control structure and a Digital signal processor (DSP) based CMOS stereo vision system was designed and built to construct an distributed embedded low cost visual guided intelligent robotic system. The intelligent fuzzy sliding mode control strategy was employed to design the robot arm and platform motion control system. The experimental results show that the proposed stereo vision algorithm has good recognition ability and accuracy. Each joint angular tracking error of humanoid robot can keep within 0.05° by using distributed FSMC controller.

Robotic intercostal nerve harvest: a feasibility study in a pig model.

The aim of this study was to report the feasibility of robotic intercostal nerve harvest in a pig model. A surgical robot, the da Vinci Model S system, was installed after the creation of 3 ports in the pig's left chest. The posterior edges of the fourth, fifth, and sixth intercostal nerves were isolated at the level of the anterior axillary line. The anterior edges of the nerves were transected at the rib cartilage zone. Three intercostal nerve harvesting procedures, requiring an average of 33 minutes, were successfully performed in 3 pigs without major complications. The advantages of robotic microsurgery for intercostal nerve harvest include elimination of physiological tremor, free movement of joint-equipped robotic arms, and amplification of the surgeon's hand motion by as much as 5 times. Robot-assisted neurolysis may be clinically useful for intercostal nerve harvest for brachial plexus reconstruction.

An Anticipatory Control for a Flexible Manufacturing System Based on the Perception of Mobile Units Using WSNs

In this paper, we design and evaluate a control system which, by using as input RSSI measures, allows anticipatory movements of robotic arms decreasing idle times at the CIMUBB Laboratory. Classical Log-Normal model, which relates the strength of a signal received by a node with the distance at which the sender of the signal is, was adopted. The hidden state of the system is determined by the Extended Kalman filter which allows us to estimate the distance and the speed of pallets moving over a closed-loop conveyor belt. From these estimates, remaining time in which the pallet will get to a stopping point near the robot is determined. This information is finally processed by a controller to determine the instant at which the robot must operate and handle the pallet. Both, a Proportional-Integral and a Fuzzy controller, were implemented and evaluated. Results show the feasibility of using wireless signals to accomplish the described goal, with some practical restrictions.

Using HMI Weintek in command of an industrial robot arm

The present paper intends to highlight the utility and importance of HMI in the control of the robotic arm, commanding a Siemens PLC. The touch screen HMI Weinteke MT3070a is the user interface in the process command of Siemens PLC, in which the distances and displacement speeds are introduced on the three axes. The interface includes monitoring robotic arm movement but also allows its command by incrementing step by step the motion over axis.

Development of a Cognitive Robotic System for Simple Surgical Tasks

The introduction of robotic surgery within the operating rooms has significantly improved the quality of many surgical procedures. Recently, the research on medical robotic systems focused on increasing the level of autonomy in order to give them the possibility to carry out simple surgical actions autonomously. This paper reports on the development of technologies for introducing automation within the surgical workflow. The results have been obtained during the ongoing FP7 European funded project Intelligent Surgical Robotics (I-SUR). The main goal of the project is to demonstrate that autonomous robotic surgical systems can carry out simple surgical tasks effectively and without major intervention by surgeons. To fulfil this goal, we have developed innovative solutions (both in terms of technologies and algorithms) for the following aspects: fabrication of soft organ models starting from CT images, surgical planning and execution of movement of robot arms in contact with a deformable environment, designing a surgical interface minimizing the cognitive load of the surgeon supervising the actions, intra-operative sensing and reasoning to detect normal transitions and unexpected events. All these technologies have been integrated using a component-based software architecture to control a novel robot designed to perform the surgical actions under study. In this work we provide an overview of our system and report on preliminary results of the automatic execution of needle insertion for the cryoablation of kidney tumours.

Toward Welding Robot With Human Knowledge: A Remotely-Controlled Approach

This paper presents a remotely controlled welding scheme that enables transformation of human welder knowledge into a welding robot. In particular, a 6-DOF UR-5 industrial robot arm is equipped with sensors to observe the welding process, including a compact 3D weld pool surface sensing system and an additional camera to provide direct view of the work-piece. Human welder operates a virtual welding torch, whose motion is tracked by a Leap sensor. To remotely operate the robot based on the motion information from the Leap sensor, a predictive control approach is proposed to accurately track the human motion by controlling the speed of the robot arm movement. Tracking experiments are conducted to track both simulated movement with varying speed and actual human hand movement. It is found that the proposed predictive controller is able to track human hand movement with satisfactory accuracy. A welding experiment has also been conducted to verify the effectiveness of the proposed remotely-controlled welding system. A foundation is thus established to realize teleoperation and help transfer human knowledge to the welding robot.

Optimizing the Robot Arm Movement Time Using Virtual Reality Robotic Teaching System

Robots play an important role in performing operations such as welding, drilling and screwing parts in manufacturing. Optimizing the robot arm movement time between different points is an important task which will minimize the make-span and maximize the production rate. But robot programming is a complex task whereby the user needs to teach and control the robot in order to perform a desired action. In order to address the above problem, an integrated 3-dimensional (3D) simulation software and virtual reality (VR) system is developed to simplify and speed up tasks and therefore enhance the quality of manufacturing processes. This system has the capability to communicate, transfer, optimize and test the data obtained from the VR and 3D environment to the real robot in a fast and efficient manner. In addition, this system eliminates the need for robot programming, and thus it is easily implemented by users with limited engineering knowledge. The optimization model is tested on a test case, in which the data are extracted from the VR system. The results show an increase in production rate and a decrease in cycle time when the make-span is minimized. The virtual reality robotic teaching system (VRRTS) offers several benefits to users, and will therefore surpass complex and time-intensive conventional robot programming methods. (Received in November 2013, accepted in June 2014. This paper was with the authors 1 month for 1 revision.)

User-defined gestures for controlling primitive motions of an end effector

In designing and developing a gesture recognition system, it is crucial to know the characteristics of a gesture selected to control, for example, an end effector of a robot arm. We conducted an experiment to collect a set of user-defined gestures and investigate characteristics of the gestures for controlling primitive motions of an end effector in human–robot collaboration. We recorded 152 gestures from 19 volunteers by presenting virtual robotic arm movements to the participants, and then asked the participants to think about and perform gestures that would cause the motions. It was found that the hands were the parts of the body used most often for gesture articulation even when the participants were holding tools and objects with both hands: a number of participants used one- and two-handed gestures interchangeably, gestures were consistently performed by the participants across all pairs of reversible gestures, and the participants expected better recognition performance for gestures that were easy to think of and perform. These findings are expected to be useful as guidelines in creating a gesture set for controlling robotic arms according to natural user behaviors.

A Method of Robotic Remote Operation Based on an Electromagnetic Tracking System

Robotic remote operation has become a new research hotspot in many fields, experiments on remote operated manipulator doing surgeries for the patients have been carried out in medical science. This paper takes the manipulator of four degrees of freedom capturing the target object as the study background and comes up with a new method of remote control for a robotic arm based on an electromagnetic tracking system which serves as the signal acquisition device. Thus the arm movement can be the input of the robot arm control loop and guides the motion of the robot arm. Firstly, the paper builds the kinematics model of the experimental robotic arm. Secondly, based on the analysis of human arm structure, the paper proposes an appropriate experimental program. Finally, experiments on remote operation have been carried out, the results of which prove the effectiveness of the method above.

Integrated Trajectory Planning and Sloshing Suppression for Three-Dimensional Motion of Liquid Container Transfer Robot Arm

For liquid transfer system in three-dimensional space, the use of multijoint robot arm provides much flexibility. To realize quick point-to-point motion with minimal sloshing in such system, we propose an integrated framework of trajectory planning and sloshing suppression. The robot motion is decomposed into translational motion of the robot wrist and rotational motion of the robot hand to ensure the upright orientation of the liquid container. The trajectory planning for the translational motion is based on cubic spline optimization with free via points that produces smooth trajectory in joint space while it still allows obstacle avoidance in task space. Input shaping technique is applied in the task space to suppress the motion induced sloshing, which is modeled as spherical pendulum with moving support. It has been found through simulations and experiments that the proposed approach is effective in generating quick motion with low amount of sloshing.

Modeling of Leadscrew using stepper motor

Recent developments on actuator in the field of mechatronics leads to customization of various applications such as precision movement of robot arm or position control either in hardness testing machine or removing a work piece from conveyor. The design of stepper motor provides a constant holding torque without need for the motor to be powered & provided that the motor is used within its limits, positioning error don’t occur, since stepper motors have physically predefined stations. This communication provides the different dynamic performance analysis of two phase bipolar permanent magnet hybrid stepper motor under no load, rated load & overload conditions along with modelling Leadscrew. The model implemented using Matlab/Simulink tool and the results analyse operating conditions for the stepper motor. The angular & linear displacement of Leadscrew are controlled by the actuator. The performance characteristics of lead screw are good with theoretical aspects