Variable Speed Electric Motor Research Articles

An electrified boom actuation system with energy regeneration capability driven by a novel electro-hydraulic unit

This paper presents a novel electrified solution for linear actuation systems, which has undergone a successful in-vehicle demonstration, marking a significant advancement in this field. Aligned with the growing trend towards electrification, this solution holds promise for a wide range of off-road applications. The showcased electro-hydraulic actuation architecture enables efficient four-quadrant operation and incorporates energy recovery capabilities. At the core of the system lies a distinctive electro-hydraulic unit, integrating a fixed hydraulic pump and a variable-speed electric motor into a compact and powerful entity. A specialized hydraulic system is designed to efficiently transform electrical energy from the electro-hydraulic unit into boom cylinder actuation. The sizing of the system is determined by the boom operation of a commercial compact loader. The maximum power output of the electro-hydraulic system is approximately 15 kW. The components of the proposed system are integrated into the reference vehicle, and comprehensive performance tests are conducted. The results of the tests performed on the vehicle with the boom lifting and lowering cycle indicate an overall system efficiency of 60%. The electrified solution consumes only about one-third of the energy used by the conventional boom actuation system on the reference machine, while exhibiting energy savings exceeding 75% during specific work phases. The energy savings come mainly from energy regeneration and minimal loss from throttling through the specialized hydraulic circuit design. The successful demonstration on the reference vehicle underscores the practicality and effectiveness of the proposed electrified solution in current mobile hydraulic applications.

Automation and Control of a Multi-feedstock Biodiesel Production Plant

The increasing need to develop renewable sources of energy to complement the energy generated via fossil fuel necessitates this study. This study demonstrates the process control and automation of a biodiesel processing plant. The developed biodiesel processing plant has a total output capacity of 200 litres per day with nine compartments divided into three major sections. The first section (pre-processing section) has the oil storage, pre-treatment, methanol and mixing tanks. The second section (main processing section) comprises of the reactor. The last section (post-processing section) comprises of the water, wash and separating tanks as well as the glycerol and biodiesel storages. The control and automation was achieved with the following components; three 3 kW variable speed electric motor, four 2.5 kW pumps, three 300 kW electric heater that are thermostatically controlled. Other materials used for the control and automation include: real time clock, Atmega328 microcontroller, LM6009 and LM 2596 modules, Liquid Crystal Display (LCD), switches, relay, LED, three temperature probes, 220 V AC alarm, four flow switches, 220 V timer relay, 220 V and 60 A contactor. Sensors are incorporated to measure the temperature, pressure, and flow level in the main reactor and the measured variables compared with the threshold values pre-set on the micro controller for control actions. The results obtained indicated that the performance of the plant was enhanced with the capacity to independently execute control actions during the biodiesel production. Thus, this study adds to the practical knowledge of system's control and automation for biodiesel production.

Performance Evaluation on the Utilization of an Established Variable Amplitude and Frequency of Vibrating Container for Potential Application in Slowing Down Sprouting in Yam

A variable amplitude and frequency of mechanical vibrating container working on cam and follower mechanism have been established. This study carried out a performance evaluation on the utilization of the established vibrating container for potential application in slowing down sprouting in yam. The vibrating container is electrically operated and a variable speed electric motor of 15, 000 rpm was selected for the machine. The performance parameters of the established mechanical vibrating container investigated were percentage maximum displacement and velocity of the vibration at different combined stages of amplitudes and frequencies. The percentage achievable maximum displacement of vibration measured for theoretical amplitude of cams of 5 mm, 10 mm and 20 mm were 89.40 %, 87.10 % and 72.7 % respectively for low frequency; 91.60 %, 88.40 % and 81.70 % respectively for medium frequency; and 93.20 %, 90.90 % and 86.50 % respectively for high frequency. The percentage achievable maximum velocity of vibration measured for theoretical amplitude of cams of 5 mm, 10 mm and 20 mm were 72.6 %, 71.40 % and 69.11 % respectively for low frequency; 79.81 %, 74.88 % and 70.96 % respectively for medium frequency; and 81.20 %, 77.52 % and 73.69 % respectively for high frequency. The results show that the established mechanical vibrating container has effective and suitable performances. The vibrator thus shows a good potential to effectively slow down sprouting when operated under load condition. It could help in slowing down sprouting in yams

Energy-Efficient Electro-Hydraulic Power Source Driven by Variable-Speed Motor

Hydraulic systems are widely used in industry due to their small size-to-power ratios and their ability to produce very large linear force and torque. In traditional hydraulic systems, a variable pump driven by an electric motor is often used as power source. In these systems, the electro-hydraulic power source always operates at its rated speed, causing lots of noise and low energy consumption, especially in no-load and light-load conditions. These problems can be solved by changing the speed of the electric motor according to the load state of the electro-hydraulic power source. In order to improve the energy efficiency of the electro-hydraulic power source and realize pressure and flow control on the basis of low cost, this paper presents the power-source structure of a variable-displacement pressure-compensated pump driven by a variable-speed electric motor; this controls the flow by adjusting the electric motor speed and controls the pressure with the variable-displacement pressure-compensated pump. However, for the variable-speed system, the starting of the electric motor with a load is relatively slow; this makes it difficult to meet the demand of flow control, and will also have a great impact on the power grid. To address these problems, a hydraulic accumulator is introduced to the inlet port of the hydraulic pump to assist in starting the pump. This method can realize the combined control of pressure, flow and power, and has high energy efficiency. This research uses experiments to verify the feasibility of the scheme, and the results show that the starting periods of the power source can be shortened from 2.8 s to 0.7 s when the load pressure is about 18 MPa. Furthermore, regarding maintaining pressure without flow outputs, the energy consumption of the designed power source can be reduced by almost 30% compared with a pure variable-displacement power source.

Razvoj i ocena performansi miksera (mešača) sa motorom za hranu

A tumble barrel food /feed mixer was designed and fabricated. It has a volumetric capacity of 0.33 m3 . The tumble barrel mixer consists of a hopper, a stainless steel barrel with baffles. It is mounted on a steel framework and driven by a shaft connected to stirrers inside the baffles. The baffles are alternatively placed in the barrel in such a way that they do not touch the stirrers during operation. The shaft is driven by a 3HP (2,25 kW) variable speed electric motor. Performance tests were conducted on the machine after fabrication using the ASAE (R2006) test standards, and also Completely Randomized Design (CRD). Three speeds of the mixer, 100,150 and 200 rpm (min-1 ) ( and four mixing times of 5,10,15 and 20 minutes were studied as they affected the Degree of Mixing (DM) of ground and shelled corn samples in the mixer. Results obtained showed, there was an increase in the degree of mixing as the speed of the machine increased from 100 to 200 rpm (min-1 ). Also the degree of mixing increased as the time of mixing increased from 5mins to 20 minutes for the three speeds studied. From the Analysis of variance tables, the calculated F-values were very much higher than the tabulated values at 5% probability. These indicate a high significance of the effect of speeds of mixing on the degree of mixing of the tumble barrel mixer. The speed of 150 rpm (min-1 ) gave the highest effect in the tumble mixer. From the difference of means tables, there were significant differences in the degree of mixing for 100 and 150 rpm (min-1 ) speeds for all the different time of mixing durations. However, in the 200 rpm (min-1 ) speed, there was no significant difference in the DM between the 15 to 20 minutes mixing time duration.

Improvement of the modeling of a hydraulic drive for exoskeleton application based on measurements

A hydraulic drive for the application to an upper limb exoskeleton is evaluated. The actuator supports the flexion of the elbow joint. The aim of the work is to analyse and characterise the electro-hydraulic drive for the application to the exoskeleton. Therefore, an evaluation of the relevant parameters of the drive is performed. These parameters are essential for the selected control strategy of the application.First, the electro-hydraulic drive is measured using a hydraulic circuit including a variable speed electric motor and a constant displacement axial piston pump producing the volumetric flow rate. The output flow characteristic of the drive is performed. A pump characterisation is derived for prescribing the motor current and knowing the corresponding volumetric pump output. A initial simulation model of the drive is compared to measurement results of the hydraulic circuit. Additional parameters are implemented into the simulation model of the pump and evaluated due to the improved simulation model, a model prediction control is possible. The measured input of the muscle tension of the wearer is taken as signal and depending on a given supporting factor the controller sets the motor current. The characterisation of the pump allows the controller to calculate the current signal of the motor in order to predict the resulting volumetric flow of the system.Second, the actuator is place onto an upper limb exoskeleton. The exoskeleton supports the elbow joint flexion during the load lifting process. The hydraulic cylinder is linked by a kinematic mechanism to the exoskeleton joint. Due to the known volumetric flow rate, depending on the motor current, the angular motion of the exoskeleton joint with the linked mechanism can be predicted. Using the signal of the muscle tension allows the setting of the exoskeleton force with the actuator input.

The low acoustic noise and turbulence wind tunnel of the University of Sao Paulo

AbstractThis paper introduces the Low Acoustic Noise and Turbulence (LANT) wind tunnel of the Sao Carlos School of Engineering, University of Sao Paulo (USP-EESC), Brazil. The closed-loop wind tunnel features several devices to improve flow uniformity, reduce swirl, and lower the background acoustic noise and turbulence, enabling stability and aeroacoustic experiments. The design criteria was based on the best practices reported, in particular for low turbulence wind tunnels. Yet, these criteria are conflicting and we discuss the decisions that had to be made and present flow quality results that were achieved. The 16-bladed axial fan with 13-blade stators is driven by a variable-speed electric motor. At the corners, 100 mm dense acoustic foam is installed on the vertical walls, floor and ceiling, and the turning vanes are filled with acoustic-absorbing material. The long settling chamber contains a 3.175 mm mesh hexagonal honeycomb and five fine mesh nylon screens, ending in a 7:1 area ratio short contraction. The 3-m long closed-working section has a $1\times 1\ {\rm m}^2$ cross-section area. At 15 m/s the working section wall boundary layer is less than 100 mm thick, providing an area of at least $800\times 800\ \mathrm{mm}^2$ where the streamwise flow uniformity was within 1%. In the 10–30 m/s flow speed range, the turbulence intensity ranged from 0.05% to 0.071% and the background acoustic noise level, obtained with an inflow microphone, ranged from 90 and 110 dB. A benchmark experiment on a flat plate boundary layer produced an almost perfect two-dimensional Blasius profile up to $Re_x \approx 2.5 \times 10^6$ . A beamforming benchmark experiment on aeroacoustics accurately identified the sound emitted by a cylinder immersed in the flow.

Benefits of enhanced techniques combining negentropy, spectral correlation and kurtogram for bearing fault diagnosis

In condition monitoring based on vibrations for rotating machines fault detection, one of the typical symptoms is the presence of repetitive transients, which are characterized by impulsive and cyclostationarity signature. The approach quite popular nowadays in the industry for their detection is time–frequency techniques. Those techniques are mainly analysis tools instead of processing tools, and in any case, they are unable to offer a versatile methodology that applies to all mechanical signals in all circumstances. On the one hand, the paper is motivated by ideas borrowed from thermodynamics, where transients are seen as departures from a state of equilibrium; it is proposed to measure the negentropy of the squared envelope (SE) and the squared envelope spectrum (SES) of the signal. On the other hand, the paper proposes an adequate approach to exploit methods such as spectral correlation and kurtogram. The work’s main objective is to investigate connections in those approaches to capture the signature of this repetitive behavior. The methodology used in this paper proposes to display as images all three proposed techniques. The impulsive events are then detected and localized in frequency by high values of the squared envelope spectrum (SES) infogram in some frequency bands. In order to analyze the signal in the frequency domain, the Short-Time Fourier Transform (STFT) is then used. The STFT is suggested in this study due to its simplicity and high flexibility. For fault, such as bearings, Kurtogram was demonstrated to be efficient. However, kurtosis based on temporal signals is effective under some conditions; its performance is low in the presence of a low signal-to-noise ratio. The paper analyzed the case of Ball Pass Frequency Inner Race (BPFI), where bearings are housed in a casing allowing the shaft to rotate while driven by a variable speed electric motor. A radial load is applied using a hydraulic cylinder, and different sizes of defects are realized. For fault like BPFI, the negentropy gives more information even for a shallow size of fault and allows a prompt fault detection, and it can also be used for fault localization. The paper demonstrated that results obtained from negentropy through infograms combining with spectral correlation could significantly extend the domain of the applicability of the Kurtogram.

Hydraulic Switching Control Supplementing Speed Variable Hydraulic Drives

Primary control of linear motion by variable speed electric motors driving a hydraulic cylinder via a constant displacement pump is an established and successful concept with a frequent use in industry. One problem arises when low or zero motion speed has to be realized under high pump pressure conditions. Such load scenarios occur frequently in certain pressing processes, e.g., for sintering or veneering. Most pumps have a lower speed limit, below which critical tribological conditions occur which impair lifespan and efficiency. In addition, pump speed control and pump fluctuation suffer from the mixed lubrication conditions in such an operation range. For a circumvention of such low speed pump operation, a digital valve control concept is presented and studied in this paper. Valve control is used in load holding phases with low speed. Pressure is provided by an accumulator which is charged by the pump in short charging cycles at reasonable pump speeds. It is shown that the mean control error during load holding phase lies within the desired band and the fluctuations of the control force are lower than those of the pump control. In addition, the unfavorable pump operation conditions can be avoided via digital control.

A high-efficient solution for electro-hydraulic actuators with energy regeneration capability

This paper proposes a cost-effective, robustly practical solution for a high-efficient electro-hydraulic actuator (EHA) for linear drives. The solution addresses the challenges of high costs and limited efficiency that limit the application of EHA for the electrification of many off-road vehicles. Based on a variable-speed electric motor and a low-cost technology for a fixed-displacement pump, the proposed solution is suitable for a compact implementation and it is capable of energy regeneration under overrunning load conditions. Two different architectures—an open circuit and a closed circuit one—are considered to determine the most practical and efficient configuration as well as the control features. Both architectures minimize throttling losses associated with the conventional regulation of hydraulic actuators. Actuator velocities below the minimum and beyond the maximum allowable pump flow rate are achieved in both architectures using a proportional valve that bypasses the pump flow. The paper describes the design methodology as well as the simulation and experimental activities performed to verify the control strategies as well as energy efficiency. Considering an EHA system of about 20 kW, a complete efficiency map of the system is determined for all the possible four quadrants of operation thus including both resistive and overrunning loads, where energy recuperation is implemented. Simulation and experimental results show that the energy efficiency of the hydraulic systems can reach 84.7% in resistive phases. In assistive phases, the hydraulic system can recover up to 81.8% of the actuator energy. The comparison between open-circuit and closed-circuit structures shows the advantages of the former in terms of energy efficiency. The proposed solution is suitable for electrified hydraulic actuation systems, in both industrial and mobile applications. With the advantages of the low cost of the hydraulic unit and high energy efficiency, it is particularly suitable for mobile applications such as construction machines, that are recently experiencing a significant electrification trend.

Design and construction of a multipurpose air screen grain cleaner

An air screen grain cleaning machine was designed and fabricated. The machine consists of the upper, the frame, the sieving unit, the blower, the outlet and the power unit. The machine was tested with a variable speed electric motor using three different grains (maize, soybean and melon) at three difference speed of 650rpm, 700rpm and 750rpm respectively. The results show that increase in the machine speed increases the machine capacity but reduces time of operation the efficient of the machine. The least efficiency of the machine was recorded to be 88% when maize was fed at 750rpm and joint highest efficiency of 94% at 650rpm when soybeans and melon were fed.

Development and Performance Evaluation of Thermostat Controlled Rotary Dryer for Agricultural Produce

Drying is ubiquitously used operation that improves on storage life of agricultural produce, either solid, liquid or slurry. Most dryers with relatively advanced technologies are expensive while the cheaper ones are manually regulated. This paper aimed at development of a direct and con-current rotary dryer that uses rolling action with hot air to effectively remove moisture from materials. The machine consists of a hopper as passage into dryer, dryer shell, heater housing, product discharge unit, shell flight, air blower for hot air distribution, thermostat for temperature regulation, temperature probe to sense the temperature from the heater as well as variable speed electric motor for power transmission. The novelty of the design is the integration of temperature regulator to the heating unit to make it thermostat-controlled. The materials for the design were selected based on strength, availability and economic value. The design calculations were done using existing machine design theories to obtain relevant design parameters. The performance evaluation showed that the machine is capable of drying various agricultural produce, say rice and yam from their initial moisture content levels of 85 and 75 % to 10 and 7 % final moisture content level respectively, at the rate of 1.2 kg/hr with the inlet air temperatures of 120° C for yam and 135 ° C for rice with humidity of 0.015. The use of machine would help to regulate drying temperature and reduce the need to manually monitor the drying process thus relieving mostly rural uses some effort in labour.

Development and performance evaluation of a liquid soap production machine for local soap industry in Nigeria

A liquid Soap production Machine was developed and evaluated to facilitate local production of liquid soap in Nigeria. A Preliminary study of the liquid soap production process was carried out within the local soap industry to collect necessary information and establish the appropriate production procedure. This was translated into the design concept of the machine. Detailed design of the components of the machine was done followed by its fabrication. The developed machine which was powered by a 1 Hp (0.746 kW) variable speed electric motor comprises a main mixer, two pre mixers, machine frame, V-belt drive and geared drive systems. All materials used in the fabrication of the machine were sourced locally. Result of machine evaluation revealed that the machine run smoothly in operation. Also, it was established that drudgery and fatigue associated with local production of liquid soap had been substantially reduced according to the responses from the users of the developed machine. The viscosity and turbidity of the liquid soap produced using the developed machine was found to be higher than that of the manually produced one while its viscosity was found satisfactorily at par with that of the liquid soap produced using one of the commercially available mixing machines (MMs). However, the cost of production of the machine developed herein and its subsequent maintenance cost is cheaper than that of the MMs.Keywords: Design, development, evaluation, liquid soap production, mixing machine

Optimization Strategies of Peripheral Speeds for Planetary Speed Reducers Used in the Actuation of Industrial Robots

Planetary speed reducers are used as the actuating module of the revolute joints for the industrial robots as a result of their specific advantages given by high transmission ratios, efficiencies and reliability. However, planetary speed reducers are currently used with variable high speed electric motors, which leads to increased peripheral speeds for the gears and planet carrier, leading in turn to increased noise during operation. Therefore it becomes necessary to manufacture the gears and planet carrier in an upper precision class, leading to significantly increased costs for the entire planetary transmission. Throughout this paper, novel solutions for planetary speed reducers are proposed, characterized by reduced peripheral speeds of the moving elements. For all the structural variants proposed, the summation method (Svamp’s rule) was applied in order to establish mathematical expressions for the transmission ratios. Subsequently, expressions for the peripheral speeds, corresponding to each moving element were derived, and expressed as a function of the number of revolutions of the input shaft. The method described in this paper was applied for each structural variant proposed, the results obtained being compared and analysed, leading to the optimal variant, characterized by a reduced level of noise and vibrations. Based on the mathematical expressions previously derived, a series of graphical representations of peripheral speeds as a function of the number of revolutions for the input shafts were elaborated for each structural variant proposed. At the same time, some recommendations useful for both designers and manufacturers of planetary speed reducers were made, based on the obtained results.

Power antenna radar with variable speed

A mathematical model of the "mains - regulated electric drive" radar antenna us with a synchronous motor with permanent magnets. Peculiarities of work at a controlled electric variable speed electric motor shaft. A method and control system with motorized adjustable mechanical and electronic scanning of the antenna, improving performance characteristics of radar stations.

On the correctness of the statement of certain issues in electrical engineering

We call attention to an incorrect use of the slip of an asynchronous electric motor as a means for adjusting its speed. A correct approach to the construction of models of a variable-speed electric motor (in particular, in the Matlab-Simulink computational environment) is proposed.

Recent developments and latest mechanical issues on variable speed large electric motor drivers for compressor trains (>50 MW)

Large variable speed electric motor drivers (above 50 MW) are required for the modern large compressor trains. Mechanical issues, latest technologies and modern developments for the large electric motors are described. New simulation procedures, findings, mitigation methods and lessons learned on the rotor-dynamic, vibration, torsional issues and coupled mechanical-electrical effects for the large electric motor drivers are discussed. A case study is presented.

Design, Fabrication, and Optimization of Jatropha Sheller

A jatropha sheller was designed, fabricated, and optimized consisting of mainframe, rotary cylinder, stationary cylinder, transmission system powered by 1kW variable speed electric motor with feasibility of manual operation. Performance evaluation considered moisture content, clearance, and roller speed as independent parameters while the responses comprised of recovery, bulk density factor, shelling capacity, energy utilization of sheller, whole kernel recovery, oil recovery, and energy utilization by extruder. Moisture contents from 9.5 to 16.5%wb failed to affect the response variables. The clearance affected the response variables except energy utilization of the extruder. The roller speed affected shelling capacity, whole kernel recovery, and energy utilization of the extruder. Optimization of shelling and extrusion operations resulted in operating conditions of 9.5%wb moisture content, clearance of 6 mm, and a roller speed of 750 rpm with acceptable quality of shelled kernels.

Experimental Procedure for Measuring the Energy Consumption of IC Engine Lubricating Pumps during a NEDC Driving Cycle

The paper presents an experimental procedure for comparing different families of IC Engine lubricating pumps in terms of total consumed energy in a NEDC driving cycle. Measures are performed on a test rig able to reproduce the oil temperature profile, the lubrication circuit permeability and its variation during the engine warm-up. The pump under test is driven by a variable speed electric motor supplying the engine velocity profile of the driving cycle. The load on the pump is generated by means of a variable restrictor controlled in a closed loop by a proper combination of speed, temperature, flow rate and pressure signals in order to replicate the typical permeability of the lubricating circuit. The method has been applied to a 15 cc/rev crankshaft mounted gerotor pump for a medium displacement Diesel engine; the flow-pressure characteristics of the lubricating circuit at different temperatures and the oil heating rate measured on the engine have been supplied to the test rig control system. The reference pump has been contrasted with a crankshaft mounted variable displacement vane pump with absolute pressure limiter device and an off-axis external gear pump with the same displacement and pressure setting. Experimental tests bring to evidence the advantage of the variable displacement pump during short trips with cold start, while the external gear pump prevails at the end of NEDC cycle where highest engine speeds and oil temperatures are reached.

Investigation of the effects of vapour quality and oil concentration on performance of a swash plate compressor

The main objective of the present study is to experimentally investigate the effects of vapour quality and oil concentration on the performance of a swash plate compressor for automotive air conditioning systems. R-134a is used as refrigerant. The compressor used is a typical automotive swash-plate-type compressor driven by a 10 hp variable-speed electric motor and lubricated by polyalkylene glycol (PAG) oil. The variables measured during the experiment are pressure, temperature, oil concentration, total mass flow rate and vapour mass flow at the inlet and outlet of the compressor. The experiment was performed at varying compressor speeds, compression ratios and vapour quality. The results revealed some unknown aspects of the compression process in an automotive air conditioning system. The vapour quality does not affect volumetric efficiency, but influences isentropic efficiency of the compressor. In the vapour quality range of 80–90%, isentropic efficiency decreases with increasing vapour quality. During the compression process, only a portion of the liquid refrigerant evaporates. However, at the outlet of the compressor, refrigerant/oil mixture never reaches steady state. The evaporation ratio decreases with increasing compressor speed, and with increasing vapour quality as well. Copyright © 2005 John Wiley & Sons, Ltd.