Single-axis Robots Research Articles

IoT-Enabled Motion Control: Architectural Design Challenges and Solutions

Ever-increasing demands for highly-efficient customized manufacturing are driving the development of Industry 4.0. Reconfigurable manufacturing systems based on modular, convertible, and interoperable equipment present a key enabler of the fourth industrial revolution. Besides suitable mechanical design, control of these smart manufacturing resources should facilitate Internet of Things (IoT) integration and reconfigurability. Existing numerical control kernels (NCK)—the major control component for motion control—hinder rapid reconfiguration due to the complexity of their monolithic centralized structure. On the other hand, reconfigurability is naturally promoted by the distributed control paradigm, as proposed by the industrial IoT (IIoT) concept; hence, in this article, we investigate design challenges in distributing the conventional centralized NCK designs used for control of computerized numerical control systems. We introduce an architecture where each axis module is augmented with a networked, IIoT-enabled low-level controller (LLC) that performs local control and exposes a network interface for communication with other LLCs toward executing the desired process. These smart manufacturing resources communicate with an edge-based high-level controller (HLC) that provides the trajectory specification over the network and schedules manufacturing tasks. We investigate real-time and network bandwidth requirements of different mappings of the NCK layers to the LLCs and the HLC, providing design-time tradeoffs for implementing IoT-ready, distributed motion control. We demonstrate feasibility of our approach using industry-grade single-axis robots and low-cost IoT microcontrollers, and show that minimal accuracy impairment is introduced compared to the centralized setup based on ISO 230 and ISO 10791-7 standards.

Digital-Twin-Based Flexibility Wires of a Circular Connector Automatic Disassembly Process

Circular connector four-core wires are created by winding in the cable; however, wires of different colors cannot be distributed fixedly within the cables. The exact positions of the four wires inside the cable cannot be determined because the cables are stripped. In addition, the core wire is flexible and can easily bend in any direction because of the external force interference. Therefore, fully automating this process is difficult. This study aimed to employ finite element analysis software to simulate the flexibility of the core wire in a four-core cable and to design a separate module that only uses a single-axis robot and a stepper motor. The core wires wound within the cable were separated by the designed separate module, which facilitated the subsequent welding process, improved the production efficiency, and reduced the labor costs.

Design of pick and place and color sorting system using VDI 2221

In order to satistfy people’s needs in Industrial era 4.0, many varieties of industrial system design have been developed especially in mechanical and automation sector. One of the examples is the pick and place system. This design aims to show the use and workings from combination of pick and place system and color sorting system. Pick and place system used is a single axis robot with two degrees of freedom and aluminium profile frame. Arduino and TCS230 sensor is used in the system. Design method uses VDI 2221 frame. The chosen design result is variant (5) with a total weighting of VDI value is 7.3175. The calculation in the design is maximum deflection calculation that occurs in the aluminium profile frame which is equal to 3.1263 x 10-18 m. The pick and place system on the x axis uses a single axis robot type KK60 lead 10 mm which is able to lift 1 kg loads and move at a maximum speed of 790 mm/s as far as 220 mm, while on the z axis uses a single axis robot type KK40 lead 1 mm which is able to lift 0.066 kg loads and move at a maximum speed of 190 mm/s as far as 30 mm. The servo motor used has a torque value of 0.48 Nm for 50 W and 0.96 Nm for 100 W.

A 3D Scanning System for Inverse Analysis of Moist Biological Samples: Design and Validation Using Tendon Fascicle Bundles.

In this article, we present the design and validation of a non-contact scanning system for the development of a three-dimensional (3D) model of moist biological samples. Due to the irregular shapes and low stiffness of soft tissue samples, the use of a non-contact, reliable geometry scanning system with good accuracy and repeatability is required. We propose a reliable 3D scanning system consisting of a blue light profile sensor, stationary and rotating frames with stepper motors, gears and a five-phase stepping motor unit, single-axis robot, control system, and replaceable sample grips, which once mounted onto the sample, are used for both scanning and mechanical tests. The proposed system was validated by comparison of the cross-sectional areas calculated based on 3D models, digital caliper, and vision-based methods. Validation was done on regularly-shaped samples, a wooden twig, as well as tendon fascicle bundles. The 3D profiles were used for the development of the 3D computational model of the sample, including surface concavities. Our system allowed for 3D model development of samples with a relative error of less than 1.2% and high repeatability in approximately three minutes. This was crucial for the extraction of the mechanical properties and subsequent inverse analysis, enabling the calibration of complex material models.

Micrometer Backstepping Control System for Linear Motion Single Axis Robot Machine Drive.

In order to cut down influence on the uncertainty disturbances of a linear motion single axis robot machine, such as the external load force, the cogging force, the column friction force, the Stribeck force, and the parameters variations, the micrometer backstepping control system, using an amended recurrent Gottlieb polynomials neural network and altered ant colony optimization (AACO) with the compensated controller, is put forward for a linear motion single axis robot machine drive system mounted on the linear-optical ruler with 1 um resolution. To achieve high-precision control performance, an adaptive law of the amended recurrent Gottlieb polynomials neural network based on the Lyapunov function is proposed to estimate the lumped uncertainty. Besides this, a novel error-estimated law of the compensated controller is also proposed to compensate for the estimated error between the lumped uncertainty and the amended recurrent Gottlieb polynomials neural network with the adaptive law. Meanwhile, the AACO is used to regulate two variable learning rates in the weights of the amended recurrent Gottlieb polynomials neural network to speed up the convergent speed. The main contributions of this paper are: (1) The digital signal processor (DSP)-based current-regulation pulse width modulation (PWM) control scheme being successfully applied to control the linear motion single axis robot machine drive system; (2) the micrometer backstepping control system using an amended recurrent Gottlieb polynomials neural network with the compensated controller being successfully derived according to the Lyapunov function to diminish the lumped uncertainty effect; (3) achieving high-precision control performance, where an adaptive law of the amended recurrent Gottlieb polynomials neural network based on the Lyapunov function is successfully applied to estimate the lumped uncertainty; (4) a novel error-estimated law of the compensated controller being successfully used to compensate for the estimated error; and (5) the AACO being successfully used to regulate two variable learning rates in the weights of the amended recurrent Gottlieb polynomials neural network to speed up the convergent speed. Finally, the effectiveness of the proposed control scheme is also verified by the experimental results.

J112023 ゴム微細表面構造の変形に伴う接触角変化の測定([J112-02]マイクロナノ理工学:nmからmmまでの表面制御とその応用(2))

Interfacial free energy of materials and micro structures on solid surface influence wetting behavior at solid-liquid interface. In this report, we have made micro surface structures on silicone rubber sheet. We consider that water contact angle on the micro structures changes as the rubber sheet deforms. The measurement system consists of specimen tensile machine composed of two single axis robots, a dispenser to put a fixed volume of droplet, and a camera for taking an image of water droplet. When micro structure was pillar with diameter of 200 [μm] and height of 200 [μm], the pitch of pillars extended as the rubber specimen extended, and water contact angle changed.

Position-based impedance control using inner servo system and its application to a desktop NC machine tool

A position-based impedance control using an inner servo system is introduced for industrial manipulators. Stiffness control, compliance control and impedance control can be easily realised. The impedance control does not have a force control mode but is the combination of position, velocity and force. The proposed impedance model force control is derived from the concept of the position-based impedance control. The force control method is applied to an NC machine tool to have a compliance. The machine tool consists of three single-axis robots with a high position resolution of 1 µm. The basic performance is demonstrated through a profiling control experiment.

Intelligent desktop NC machine tool with compliant motion capability

In this paper, a new desktop NC machine tool with compliance control capability is presented for finishing metallic molds with small curved surface. The NC machine tool consists of three single-axis robots. Tools attached to the tip of the z-axis are ball-end abrasive tools. The control system of the NC machine tool is composed of a force feedback loop, position feedback loop and position feed-forward loop. The force feedback loop controls the polishing force consisting of tool contact force and kinetic friction force. The position feedback loop controls the position in pick feed direction. Further, the position feed-forward loop leads the tool tip along cutter location data. In order to first confirm the application limit of a conventional industrial robot to a finishing task, we evaluate the backlash that causes the position inaccuracy at the tip of an abrasive tool, through a simple position/force measurement. Through a similar measurement and a surface following control experiment along a lens mold, the basic position/force controllability with high resolutions is demonstrated.

2A1-B06 コンプライアンス特性を有する直交型ロボットの開発と微小曲面金型仕上げへの適用実験

A new orthogonal-type robot with compliant motion capability is presented for finishing metallic molds with small curved surface. The orthogonal-type robot consists of three single axis robots with a position resolution of lynm. A small ball-end abrasive tool is attached to the tip of z-axis of the robot. The control system of the orthogonal-type robot is composed of a force feedback loop, a position feedback loop and a position feedforward loop. The effectiveness of the orthogonal type robot is examined through an actual finishing test of a LED lens mold with a diameter of 4 mm.

THE INFLUENCES OF ARM RESIST MOTION ON A CAR CRASH TEST USING HYBRID III DUMMY WITH HUMAN-LIKE ARM

Safety of the occupant during the crash is very essential design element. Many researches have been investigated in reducing the fatal injury of occupant. They are focusing on the development of a dummy in order to obtain the real human-like motion. However, they have not considered the arm resist motion during the car accident. In this study, we would like to suggest the importance of the reactive force of the arm in a car crash. The influences of reactive force acting on the human upper extremity were investigated using the impedance experimental method with lumped mass model of hand system and a Hybrid III dummy with human-like arm. Impedance parameters (e.g. inertia, spring constant and damping coefficient) of the elbow joint in maximum activation level were measured by free oscillation test using single axis robot. The results showed that without seat belt, the reactive force of human arm reduced the head, chest, and femur injury, and the flexion moment of the neck is higher than that of the conventional dummy.

Development of a three‐dimensionally movable phantom system for dosimetric verifications

The authors developed a three-dimensionally movable phantom system (3D movable phantom system) which can reproduce three-dimensional movements to experimentally verify the impact of radiotherapy treatment-related movements on dose distribution. The phantom system consists of three integrated components: a three-dimensional driving mechanism (3D driving mechanism), computer control system, and phantoms for film dosimetry. The 3D driving mechanism is a quintessential part of this system. It is composed of three linear-motion tables (single-axis robots) which are joined orthogonally to each other. This mechanism has a motion range of 100 mm, with a maximum velocity of 200 mm/s in each dimension, and 3D motion ability of arbitrary patterns. These attributes are sufficient to reproduce almost all organ movements. The positional accuracy of this 3D movable phantom system in a state of geostationary is less than 0.1 mm. The maximum error in terms of the absolute position on movement was 0.56 mm. The positional reappearance error on movement was up to 0.23 mm. The observed fluctuation of time was 0.012 s in the cycle of 4.5 s of oscillation. These results suggested that the 3D movable phantom system exhibited a sufficient level of accuracy in terms of geometry and timing to reproduce interfractional organ movement or setup errors in order to assess the influence of these errors on high-precision radiotherapy such as stereotactic irradiation and intensity-modulated radiotherapy. In addition, the authors 3D movable phantom system will also be useful in evaluating the adequacy and efficacy of new treatment techniques such as gating or tracking radiotherapy.

Robust digital friction compensation

Even though the nonlinear compensator proposed by Southward, et al. can guarantee the closed-loop stability for stick-slip friction systems in continuous-time control, applying this to digital control systems may often generate a limit cycle response in the vicinity of a reference position because of the inherent time delay of sample-and-hold operation. In this paper, a new robust digital friction compensator (RDFC) is proposed, which consists of a digital P controller+hysteresis friction compensator part (position feedback loop) and an analog D controller part (velocity feedback loop). The hysteresis compensator in the position feedback loop increases the phase lead in comparison with Southward’s technique such that the phase lag coming from the time delay of digital control can be compensated for. A modified form of Lyapunov’s stability theorem is employed to verify the asymptotic stability of the RDFC. Stability and control effectiveness are verified analytically and experimentally on a single-axis robot system.

Experimental results for the end-effector control of a single flexible robotic arm

Various control schemes for a single flexible robot arm are considered in this paper. They require a limited amount of on-line computations. All trials are performed on the physical process and embody a conclusive, although partial, comparison for this kind of single axis robot. They are representative of some major applied research directions which captured the attention of many researchers throughout the 1980's. Some general conclusions are derived. >