Secure Clamping of Parts for Disassembly for Remanufacturing

Robot based remanufacturing of valuable products is commonly perceived as promising field in future in terms of an efficient and globally competitive economy. Additionally, it plays an important role with regard to resource-efficient manufacturing. The associated processes however, require a reliable non-destructive disassembly. For these disassembly processes, there is special robot periphery essential to enable the tasks physically. Unlike manufacturing, within remanufacturing there are End-of-Life (EoL) products utilized. The specifications and conditions are often uncertain and varying. Consequently the robot system and especially the periphery needs to adapt to the used product, based on an initial examination and classification of the part. State of the art approaches provide limited flexibility and adaptability to the disassembly of electric motors used in automotive industry. Especially the geometrical shape is a limiting factor for using state of the art periphery for remanufacturing. Within this contribution a new kind of flexible clamping device for the disassembly of EoL electrical motors is presented. The robot periphery is systematically developed regarding the requirements stemming from the remanufacturing approach. It consists of three clamping units with moveable pins. Utilizing two linear axes, a two dimensional working space is realized for clamping the parts depending on their conditions and shape.

Rotor Position Synchronization in Central-Converter Multi-Motor Electric Actuation Systems

The aerospace industry is increasingly transitioning from hydraulic and pneumatic drives to power-electronic based drive systems for reduced weight and maintenance. Electromechanical thrust reverse actuation systems (EM-TRAS) are currently being considered as a replacement for mechanical based TRAS for future aircraft. An EM-TRAS consists of one or more power-electronic drives, electrical motors, and gear-trains that extend/retract mechanical members to produce a drag force that decelerates the aircraft upon landing. The use of a single (“central”) power electronic converter to simultaneously control a set of parallel induction machines is a potentially inexpensive and robust method for implementing EM-TRAS. However, because the electrical motors may experience different shaft torques—arising from differences in wind forces and a flexible nacelle—a method to implement rotor position synchronization in central-converter multi-motor (CCMM) architectures is needed. This paper introduces a novel method for achieving position synchronization within CCMM architecture by using closed-loop feedback of variable stator resistances in parallel induction machines. The feasibility of the method is demonstrated in several case studies using electromagnetic transient simulation on a set of parallel induction machines experiencing different load torque conditions, with the central converter implementing both voltage-based and current-based primary control strategies. The key result of the paper is that the CCMM architecture with proposed feedback control strategy is shown in these case studies to dynamically drive the position synchronization error to zero. The initial findings indicate that the CCMM architecture with induction motors may be a viable option for implementing EM-TRAS in future aircraft.

Impact of a Punching Process on the SyRM Iron Loss: SPICE Model as an Effective Tool for Iron Loss Modeling

Many technologies for cutting the magnetic laminations, from which electric motors cores are built, change material properties, among which are magnetizability and iron loss, thus affecting the motor parameters such as motor efficiency. This problem is particularly important for low-power motors, in which the dimensions of the magnetic circuit elements are relatively small. The correct estimation of the motor efficiency is important as early as at its design stage. This is possible when the correct material characteristics are used. This knowledge and analytical model enabling fast estimation of material properties (depending on the actual size) are necessary for engineers, who design electrical motors by analyzing many solution variants in a short time. The author proposes an analytical model of changing material properties, implemented in SPICE software. Its effectiveness was compared with measurement results while being a competitive solution in relation to other analytical models. The proposed SPICE model allowed evaluating material properties for lamination of any width. In the end, the knowledge concerning the material properties was used to calculate the iron loss in the stator of the SyRM motor, showing the need to use the material characteristics calculated for the specified width of the core piece.

Multibody system simulation as a predictive tool for possible estimation of negative effects caused by vibrations of FDM device

The design of fused deposition modeling (FDM) devices in their current form is associated with many negative effects, which result mainly from their construction deficiency. Due to the constant effort to increase the accuracy and speed of these devices, we often encounter the emergence of various negative factors. One of the most significant factors is the presence of negative vibrations of the frame and individual components. These are directly linked to several shortcomings that FDM devices come with. Efforts to make the structures as simple as possible, their low weight or the use of filament extruders placed directly on the printheads and axis travels, are perceived as well-known shortcomings. These negative phenomena are subsequently manifested by the emergence of specific defects visible on the surface of the manufactured models. The article presents the possibility of predicting the occurrence of these negative phenomena, with the use of multibody simulation. This simulation analyzes the movements of a specific device at different print speeds. The article then presents the results of these simulations and analysis of the transmission of negative oscillations at specific critical points of the FDM device. Finally, the article examines the influence of possible regulation of devices acceleration rates caused by electrical motors in individual axes and their influence on the final surface quality of the manufactured model. The article points out the possibilities of using this type of simulation processes and analysis in the design process of new types of frames and translation mechanisms for FDM devices.

Decoupled Multi-Loop Robust Control for a Walk-Assistance Robot Employing a Two-Wheeled Inverted Pendulum

This paper develops a decoupled multi-loop control for a two-wheeled inverted pendulum (TWIP) robot that can assist user’s with walking. The TWIP robot is equipped with two wheels driven by electrical motors. We derive the system’s transfer function and design a robust loop-shaping controller to balance the system. The simulation and experimental results show that the TWIP system can be balanced but might experience velocity drifts because its balancing point is affected by model variations and disturbances. Therefore, we propose a multi-loop control layout consisting of a velocity loop and a position loop for the TWIP robot. The velocity loop can adjust the balancing point in real-time and regulate the forward velocity, while the position loop can achieve position tracking. For walking assistance, we design a decoupled control structure that transfers the linear and rotational motions of the robot to the commands of two parallel motors. We implement the designed controllers for simulation and experiments and show that the TWIP system employing the proposed decoupled multi-loop control can provide satisfactory responses when assisting with walking.

Modeling of high frequency high voltage of waveforms on life of enamel insulation

<p>In recent years it has been observed that insulation failure in electrical motors is caused by adjustable speed drives fed by power electronic converters. These converters produce impulse waveforms having a high slew rate generated by the high switching frequency of IGBTs. This paper focuses on high switching frequency stress in low voltage electrical motors for adjustable speeds. To examine the motor winding insulation under such stress twisted-pair samples were developed from enameled wires. A single-coated polyester of enamel with a thickness of 40 microns is used for this work. High-frequencies, high voltages of Square, and Square-rising, Square-spike waveforms of 10-30 kHz are used here. The test results show that the insulation fails earlier for the Square waveform compared to the Square-spike and Square-rising waveforms. In a nutshell, there is an analysis of PD formation in the insulation system at a higher switching frequency is analyzed. Electric field distributions between twisted pairs with various air gaps of the insulation system stressed by the Square and Square-rising waveforms up to 30 kHz are modeled using COMSOL software.</p>

Modelling of Stator Coil–To–Ground Faults in Induction Motor

Three–phase squirrel cage induction motors are the most widespread types of electrical motors which can be found in both industrial and tertiary applications. There are some reasons why they are so often used, such as simple construction, nearly maintenance-free, advantageous price and the possibility to feed them directly from the AC network. Even if their reliability is very high, some unexpected breakdowns can occur during their operation. In this paper, coil–to–ground faults of motor stator winding have been taken into consideration. These failures have been modelled in several points of one stator phase using COMSOL software. As seen from simulation results these failures have a significant impact on current distribution in stator phases causing changes in rotor currents, motor inner torque, speed, etc., depending strongly on the actual point of the failure.

Simulation of the movement of the supporting leg of an exoskeleton with two links of variable length in 3D

A two-link model of exoskeleton with variable-length links for supporting the lower limbs of the human musculoskeletal system is proposed in the article. The researched model differs from the existing ones by the variable-length links, and by the angle calculation method. While in the existing models, the angles are calculated from the regular direction – from vertical, or from horizontal, – in the proposed research they are calculated between the links. As for practical exoskeleton implementation, the proposed method of angle calculation is appropriate to the actual working conditions of the electrical motors with the reduction gears installed in the hinges, which change the angles between the links. The construction of a variable-length exoskeleton link consists of two absolutely solid weighty sections located at both ends of the link and one weightless section between them in the center of the link. In the weightless section, there is a drive that creates a control longitudinal force, which realizes the increase or decrease in the length of the link in the required manner and provides the necessary maintenance of the length of the link when the person moves in the exoskeleton. The links are connected to each other using spherical hinges. Drives are installed in each hinge, creating control torques, which provide a relative rotational movement of the links. The jointly controlling longitudinal forces and moments realize the maintenance of the posture or the movement of the link in the required manner and, in relation to the exoskeleton, the repetition of the basic biomechanical properties of the human musculoskeletal system. The mathematical model in the form of the system of Lagrange differential equations of the second kind is obtained. The obtained mathematical model is examined for existence and uniqueness of the Cauchy solution. The kinematic trajectory of the link motion has been synthesized, which simulates the anthropomorphic movement of the supporting leg during the single-support phase of movement, and the control actions required for its implementation has been found. The significance of the results obtained in the process of modeling lies in the ability to create active exoskeletons, prostheses in medicine, anthropomorphic robots, and spacesuits that take into account the biomechanical features of the functioning of the human musculoskeletal system.

Multi-Link Magnet Device with Electromagnetic Manipulation System for Assisting Finger Movements with Wireless Operation

We introduce a new mechanism and control system for wireless assistive finger training. The proposed mechanism and control system can provide natural finger flexion and extension via magnetic force and torque between a driving coil and a multi-link magnetic assist device placed on the fingers. The proposed mechanism is designed to allow normal movement while maintaining a natural finger shape, even when multiple magnets are applied to the fingers. Anatomical features were considered in the design to accommodate the angular changes between the fingers during hand extension and flexion. The magnetic force between the control system and the device on the hand allows extension and flexion of the fingers without the use of wires and electrical motors. The performance of the driving system and the magnetic device were verified through various simulations and experiments. A control program with motion tracking is also developed using LabView software. Hence, a wireless assistive finger training system is successfully realized.

Optimization of torque ripples in direct torque control drives

The article discusses the features of the synthesis of a hybrid method for commutation of a three-phase inverter in a classic version of drives with direct torque control (DTC), which involves the use of relay characteristics in the flux- and torque control blocks. It is proved that the output voltage of a converter based on a B6-inverter formed by only six basic vectors (excluding the zero vector) limits further optimization of flux- and torque ripples in the electrical motors. It has also been proven that with the classical drives with direct torque control, the torque ripples on the motor shaft are indeed higher than in systems with pulse width modulation. An analysis of the method was carried out which could allow reducing the amplitude of the torque ripples when drives with direct torque control are applied for motors supplied with only basic vectors of the inverter due to the modified (hybrid) method of inverter commutation. The conditions under which the hybrid control method of the inverter is really capable of reducing the amplitude of the motor flux- and torque ripples are considered. Based on the analysis of the proposed solution, the law of hybrid control of the inverter is presented by means of the formation of additional vectors of its output voltage via basic vectors of the inverter. The advantages of the method include the simplicity of drive control under development or in the existing drive control system, the implementation of which is carried out exclusively by a software product. With the absence of iterative methods of mathematics, the resources of microprocessor control units are reduced, which makes this method even more attractive in low-budget electrical drives that do not claim to be "high-end" of control blocks. The oscillograms are shown of a flux and current of motor with direct torque control motor application only with six base vectors of the output voltage of a semiconductor inverter and a drive with direct torque control by the hybrid method with additional voltage vectors based on the basic vectors of the inverter.