Sensorless Torque Research Articles

Finite-Time Control for Dual Three-Phase Hybrid Excitation Synchronous Machine Based on Torque Sensorless Current Coordinative Strategy

In this paper, the finite time speed regulation problem is investigated for a dual three-phase hybrid excitation synchronous machine (DTP-HESM) without a torque meter. The electromagnetic torque estimation required in the current coordinative strategy is obtained through the disturbance estimation technology. This method increases fault tolerance and reduces the cost as well as complexity of the DTP-HESM system. In contrast to the existing controllers in the speed loop, the non-singular terminal sliding mode control method is adopted to ensure the finite-time convergence of speed tracking in the whole speed region. To achieve better dynamic performance in the presence of lumped disturbances, including unknown load torque and unmodeled dynamics, the disturbance estimations are introduced into the sliding mode variable to establish a composite speed regulating controller. Simulations and experiments are carried out to validate the feasibility and effectiveness of the proposed control scheme.

Sensorless torque and power measurement in DC electric drive

Purpose. Determination of the resistance torque and power on the working body of the executive mechanism of the DC electric drive in order to increase the efficiency of the working body by maintaining and stabilizing the flow of mechanical power on the motor shaft at a constant level. the features of the construction and operation of specific technological mechanisms for which it is necessary to determine the torque of resistance and power on the working body of the executive mechanism. The possibilities of sensorless measurement of mechanical parameters of direct current drive systems are investigated. The resistance torque and power on the working body of the executive mechanism of the DC electric drive in order to increase the efficiency of the working body by maintaining and stabilizing the flow of mechanical power on the motor shaft at a constant level are determination. With this approach, the working capacity of the working body increases due to the maintenance and stabilization at a constant level of the flow of mechanical power on the engine shaft. Achieving the maintenance of power at a constant level allows one to implement "soft" mechanical characteristics on the working body of the drive, which under certain conditions allows one to take into account the technological features of work and increase the efficiency of the technological tool. The methods. The study was carried out on the basis of the ideas of modal synthesis of the observing device. According to this technique, an estimate for the state vector of the surveillance system is found. The state assessment was carried out on the basis of information about the input and output values of the system and its structure, which are known a priori. The use of a matrix mathematical apparatus made it possible to find the initial equations describing the dynamic processes in the control object. Findings. On the basis of direct measurements of the operating values of the voltage and current of the DC drive motor, the mechanical parameters of the technological process, such as the mechanical moment of resistance and active power on the working body, are determined, according to which the control system is synthesized and the power flow is stabilized in the working area. The originality. The dynamic parameters of the control system are set, which allow controlling the flow of mechanical power on the working body of the drive engine based on the specified torque of resistance. Practical implementation. The use of a synthesized control system allows you to reliably determine the mechanical parameters of the technological process, stabilize them at an acceptable level, which will increase the efficiency of the working body. Having determined the mechanical parameters of the technological process, it is possible to synthesize a control system with torque and power regulators, which will lead to soft mechanical characteristics.

Overview of Fundamental Frequency Sensorless Algorithms for AC Motors: A Unified Perspective

This article uses the active flux concept to review fundamental frequency sensorless algorithms for both induction and permanent magnet motors in one framework. Fundamentally, sensorless torque estimation can be directly solved using voltage-current model (VM) estimator or indirectly solved using current-speed model (CM) estimator. The latter turns the torque estimation problem into a speed estimation problem. The stator flux in VM and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> -axis angle in CM are deemed as the two sets of original states for the sensorless drive. Through the change of states, the direct torque estimation can be realized via observer designs, whereas the speed dependency in the dynamics of the unknown state [e.g., active flux and electromotive force (emf)] gives rise to a class of speed estimation methods, known as model reference adaptive system (MRAS). The idea of a general speed observer is proposed to summarize various separate speed estimation methods needed for direct torque estimation. It is suggested to adopt inherently sensorless designs such that two-way coupling between torque estimation and speed estimation is avoided. For induction motors, it turns out that the unmodeled voltage in the active flux dynamics reveals current flowing in rotor bars and can be further modeled, for which the solutions to regeneration instability problem are discussed, and change of states is recommended to attain global stability. Finally discussed are the results of the slow reversal test, where local weak observability of ac motors can be potentially preserved.

Practical torque sensorless super-twisting control of manipulators based on a novel integral non-singular fast terminal sliding mode with fixed-time convergence

ABSTRACT In this paper, a robust controller has been proposed for first-order uncertain non-linear systems by introducing a novel hybrid sliding surface. Using this method, contrary to previous proposed sliding surfaces, the state trajectory begins moving on the correct sliding mode and the reaching phase can be reduced to the minimum time. Thus, the transient response speed of the system and consequently the efficiency and robustness of the system increase. Moreover, the convergence of the system state in bounded time, independent of the initial conditions of the system, is guaranteed without singularity problems. Then, for torque sensorless control of permanent-magnet DC motors, as one of the most prevalent joint actuators in robotics, an adaptive super-twisting controller, based on the proposed hybrid sliding surface, has been presented. Using this method, continuous finite-time control of the DC motor’s torque without a torque sensor is realized. The DC motor load-side torque is estimated based on an adaptive wavelet neural network and it is compensated in the control loop. In addition to the stability proof and fixed-time convergence of control schemes, a set of simulation and experimental studies have been provided to evaluate the efficiency of control algorithms and investigate their feasibility.

Sensorless torque and flux control of induction motor fed by photovoltaic system

This paper presents a new direct torque and flux control method for induction motor fed from Photovoltaic (PV) System. The proposed strategy is based on Stator Field Orientation with deadbeat torque and flux control. The deedbeat control approach is based on establishing the voltage vector necessary to supply the motor and reach the electromagnetic torque and flux references at the end of a sampling period T. In order to create the voltage shape and frequency to control the induction motor, the inverter is supplied by a DC voltage extracted from a PV system. Model Reference Adaptive System and Luenberger Observer are designed to determine the stator flux and rotor speed. Extensive simulation work was carried out, which demonstrated that the proposed strategy is capable of reducing the torque and flux ripples and maintaining a constant switching frequency.

Algorithm for the torque sensorless worm gearbox servo application based on kinetic motion/friction realization

This paper provides an effective systematic procedure for the efficient treatment of worm gearboxes for industrial-grade cases. The accurate and general dynamic model of the worm gearbox is analytically obtained and the effects of the dominant factors, such as the disturbance torque and friction between the teeth and threads, are also addressed. A universal algorithm is proposed for accurate estimation of the disturbance torque that makes no utilization of any designated sensing unit. Numerous experimentations have been conducted to validate the proposed procedure and algorithm. The contributions of this paper are not limited to worm gearboxes but rather are extendable to all other conventional gearboxes that use similar power transmission methods. The gradient patterns of the normal force, the friction force, and the coefficient of friction in worm gearboxes are also identified as a function of the effective elements, such as the output loading torque and angular velocity.

Analysis of Instability in Torque Control of Sensorless PMSM Drives in Flux Weakening Region

This article analyzes the effect of angle estimation error on the sensorless torque control of the permanent-magnet synchronous motor (PMSM). The actual torque of PMSM may differ from the torque reference due to the angle error in sensorless control. Furthermore, this torque discrepancy can cause instability to the control system, especially in the flux weakening region. The instability is highly dependent on the gain setting of the controller and observer in the control loop. To mitigate the adverse effect of the angle error, a torque feedforward method considering the transient angle error is proposed. With the proposed torque feedforward method, the gain margin of the control loop can be enhanced without modifying the gain of the control system. The proposed method is verified through the simulation and experimental results.

Simplified Sensorless Torque Estimation Method for Harmonic Drive Based Electro-Mechanical Actuator

Torque measurements can significantly enhance control and monitoring loops for many mechatronic and aerospace applications. A typical challenge is to justify incorporating a torque sensor in terms of cost, system complexity, and reliability. Recently, sensorless torque estimation methods have been developed for robotic joints that include harmonic drive transmissions (HDTs). The principle is based on their relatively low torsional stiffness, which allows for estimating the transmitted torque by measuring the torsional angles (via existing joint encoders) and a compliance model. However, these methods are based on nonlinear models that are difficult to identify and tune. In this study, a simplified torque estimation method is introduced based on the structural damping friction of the HDTs. The structural damping can be correlated to the HDT torque using a simplified linear dynamic model and torsional rate measurements. Experimental results have validated the proposed method, using a robotic joint setup with an external torque sensor that has been previously utilized for testing several torque estimation methods.

A Redundant Manipulator Joint Torque Estimation Method Based on Disturbance Observer

With the continuous development of the robot industry, both industrial robots and collaborative robots are developing towards light type and intelligence. The core issue is that how to improve the dynamic control performance of robots and reduce costs. The accurate torque feedback control can be achieved by introducing a joint torque sensor. The disadvantages brought by it are higher cost and the limited performance of the torque sensor. Therefore, on the basis of the traditional current estimated torque, combined with the accurate joint torque data fed back by the torque sensor, a method to estimate the harmonic transmission torque in the joint based on the disturbance observer is proposed, and a joint torque model is constructed. At the same time, the compensation factor is introduced to improve the accuracy of torque estimation. In the method proposed in this paper, the theoretical position and actual position, speed difference and motor current of the dual encoder on the motor side and the link side are used to estimate the harmonic transmission torque through the disturbance observer, and the corresponding coefficient is identified. By calibrating the transmission error compensation term and friction force with the torque sensor, the joint torque estimation model is obtained, and the sensorless joint torque estimation can be realized. This method does not require additional torque error compensation caused by harmonic drive deformation in the controller. Therefore, the torque control method without torque sensor is adopted in batch, which is not affected by the configuration and dynamic parameters of the manipulator. In the experiment, the output data of the joint torque sensor is used for testing and comparison. Through the single joint and redundant robot manipulator integration testing, the effectiveness of the proposed joint torque estimation method is verified.

An improved torque sensorless speed control method for electric assisted bicycle with consideration of coordinate conversion

In this paper, we propose an improved torque sensorless speed control method for electric assisted bicycle, this method considers the coordinate conversion. A low-pass filter is designed in disturbance observer to estimate and compensate the variable disturbance during cycling. A DC motor provides assisted power driving, the assistance method is based on the real-time wheel angular velocity and coordinate system transformation. The effect of observer is proved, and the proposed method guarantees stability under disturbances. It is also compared to the existing methods and their performances are illustrated through simulations. The proposed method improves the performance both in rapidity and stability.

A Position Sensorless Torque Control Strategy for Switched Reluctance Machines With Fewer Current Sensors

To decrease the cost, enhance the torque performance, and improve the system reliability, this article puts forward a novel position sensorless torque control strategy for switched reluctance machines (SRMs) with fewer current sensors. In this article, a developed direct torque control (DTC) strategy is proposed for the torque ripple mitigation, where a hybrid chopping mode is employed and the torque is online compensated according to the torque error. A developed current-sensing scheme with fewer current sensors is presented. The phase current in a whole period can be easily detected for both the torque control and sensorless control. The position sensor is removed from the proposed drive. The real-time rotor position of each phase can be obtained by implementing a flux linkage-current-based method. According to the current and position, the instantaneous phase torque and torque sharing function can be determined for the DTC. Therefore, system reliability can be significantly improved due to the simplified sensor part. With the proposed scheme, a compact, high-reliable, and high-performance SRM drive can be achieved. A three-phase 12/8 SRM prototype is employed for the experiment to verify the feasibility of the proposed system.

Haptic Augmentation Towards a Smart Learning Environment: The Haptic Lever Design

This paper presents the design of a haptic interface called the Haptic Lever, to show four force-related phenomena for haptic augmentation towards Smart Learning Environments. The Haptic Lever is a mechanism with a sensorless torque control developed by means of a Disturbance Observer (DOB) to render forces that allow users to feel virtual phenomena. The control response converges in the torque reference as a result of a gain calibration and the DOB response. The Haptic Lever was evaluated experimentally with four dynamic models for constant (membrane), linear (Hook’s law and viscous damping), and exponential (Coulomb’s law) haptic augmentation. In the first experiment, the user can feel a constant force when passing between two reference points and feel resistance while moving through a virtual membrane. In the second and third experiment, the user can feel and interact with the linear dynamic models of Hook’s law and viscous damping, in the form of a compression or tension spring by pushing or pulling them, respectively. Finally, in the fourth experiment, the user can feel an attraction or repulsion force between two virtual point charges that follows the exponential dynamic model of Coulomb’s law. The results obtained from the experiments showed that the Haptic Lever successfully rendered the equivalent forces to each virtual phenomenon. The haptic sensation is estimated in terms of the torque response under a profile determined by the dynamic models. From the experimental results, it can be observed that the torque in $Nm$ corresponded to each represented phenomenon.

A STUDY OF MRAS BASED SPEED ESTIMATION OF SENSORLESS INDUCTION MOTOR USING MATLAB AND SIMULINK MODELLING

Model reference adaptive system(MRAS) based techniques are one of the best method to estimate the rotor speed due to its performance and straight forward stability approach.These techniques use two different models which have made the speed estimation a reliable scheme especially when the variations.The scheme use the stator equation and rotor equation as the reference model and the adjustable model respectively.The output error from both models is tuned using a PI controller yielding the estimated rotor speed.It presents the identification and parameter estimation of an induction motor model with parameters varying as functions of the operating conditions. A Sensorless torque control system for induction motors is developed. The system allows for fast and precise torque tracking over a wide range of speed.The induction motor is controlled through field orientation techniques that require knowledge of the rotor speed.Since speed sensors decrease the reliability of a drive system (and increase its price), a common trend in motor control is to use an observer to estimate speed.

A STUDY OF MRAS BASED SPEED ESTIMATION OF SENSORLESS INDUCTION MOTOR USING MATLAB AND SIMULINK MODELLING

Model reference adaptive system(MRAS) based techniques are one of the best method to estimate the rotor speed due to its performance and straight forward stability approach.These techniques use two different models which have made the speed estimation a reliable scheme especially when the variations.The scheme use the stator equation and rotor equation as the reference model and the adjustable model respectively.The output error from both models is tuned using a PI controller yielding the estimated rotor speed.It presents the identification and parameter estimation of an induction motor model with parameters varying as functions of the operating conditions. A Sensorless torque control system for induction motors is developed. The system allows for fast and precise torque tracking over a wide range of speed.The induction motor is controlled through field orientation techniques that require knowledge of the rotor speed.Since speed sensors decrease the reliability of a drive system (and increase its price), a common trend in motor control is to use an observer to estimate speed.

Development and testing of an efficient and cost-effective underwater propulsion system

Underwater vehicle propulsion performed by exploiting electrical motor is in general the most flexible solution and it is growing in popularity because of its high efficiency both at high and at low advance speed, quick and simple deployment, low costs, and encumbrance. In the present work, permanent magnet synchronous motors for underwater propulsion are proposed. In particular, advanced sensorless control techniques of permanent magnet synchronous motors permit reduced costs, high reliability, and performances. When dealing with small autonomous underwater vehicle propulsion, such devices are hard to find in the market. Hence, the authors focused the research in the development of a system able to perform a reliable rotational speed and torque sensorless estimation. The design and implementation of a complete solution for underwater propulsion are presented as well as a novel rotor polarity identification technique exploiting a high-frequency injection control. Pool tests for the identification of the performances and of the dynamic parameters of the propulsion system are presented. Finally, the possibility of operating a sensorless estimation of the thrust and torque exerted by the propeller and pool test measurements are presented. These features could be exploited to improve navigation accuracy and involves obvious benefits in terms of cost reduction and reliability of the system.

Power-assist control of a human–electric hybrid bicycle with energy regeneration and cruise control

In this article, we propose three different controllers for the human–electric hybrid bicycle. The main objective of the controller is to ensure power-assist, cruise control and regenerative braking whenever possible. Power-assist controller is designed without torque sensor, cruise controller is designed to keep constant speed and the regenerative braking controller is designed to save the energy while braking. Proportion-assisted power method is implemented using the pedaling torque estimated by disturbance observer. Cruise control is achieved using the estimated speed from the hall sensor rather than using actual speed sensor. Single switch regenerative braking method is applied to yield maximum energy recovery during braking. It is noted that the performance similar to torque sensor–based proportion-assisted power is achieved using torque sensorless approach. All of the proposed controllers are implemented experimentally in the experimental setup, and their results are presented.

Sensorless Torque Control of an Induction Motor through Quadrature Voltage Injection

A previously reported sensorless torque control method for induction motors uses a high-frequency voltage injection signal on the direct axis and a demodulation based on the root-mean-square filter to estimate the rotor flux angle. Further investigations evidence that the quadrature voltage injection has advantages over the direct axis voltage injection due to the high-frequency characteristics of the motor's magnetic circuit. In this paper, the previously proposed method is further developed, using a post-processing low-pass filter to eliminate the need of root-mean-square filters. It is shown that the response of the changes of high-frequency impedances to the injected signal behave like an amplitude modulation, and the design of the post-processing is briefly discussed. Practical experiments comparing the reference and the measured torques are presented.

Adaptive TSK fuzzy sliding mode control design for switched reluctance motor DTC drive systems with torque sensorless strategy

This study proposes a novel Adaptive Takagi-Sugeno-Kang (TSK) Fuzzy Sliding Mode controller (abbreviated as AFSC) and investigates the application for a switched reluctance motor (SRM) direct torque control (DTC) drive system without a torque sensor. The sliding mode controller (SMC) is used for reducing the influence of uncertainties and external disturbances, and it performs fast responses. The parameters of the adaptive TSK fuzzy controller (AFC) are adjusted online for further reducing error residues after applying the SMC. Lyapunov stability theory is used for deriving the stability condition of the SMC and the adaptive update law of the AFC. The stability of the overall closed-loop system is also analyzed. To verify the performance and practicality of the controller developed for this study, the AFSC is employed as the speed controller in a SRM DTC drive system. The experimental results reveal that the steady-state speed error is maintained between ±2 rpm when the motor load torque is 1 Nm, and the motor operates at low, medium, high, and variable speeds. Comparing with the conventional SMC, a faster and smoother speed and torque responses are achieved. Moreover, the proposed control strategy is superior to the conventional SMC with respect to robustness for external disturbances.

Discrete Sine and Cosine Transforms for Signal Processing Spectral Overlap Saliencies of Induction Machine

A novel separation procedure applied to overlap condition of saliencies in induction machine is presented. The machine's current reaction to voltage step excitation is used to obtain saliency signals. The proposed procedure is based on a digital signal processing implementation of the discrete sine and cosine transforms for extracting the slotting saliency signal at close and equal frequencies of the slotting and saturation saliencies under heavy load operation. The proposed algorithms are processed based on an online adaptive threshold. Using the proposed separation algorithm guarantees precise estimation of rotor/flux angle and efficient sensorless control of the induction machine. A sensorless induction motor drive is implemented in the laboratory. Extensive experimental results are presented. A performance comparison between the proposed algorithm and previous works is provided. The robustness and effectiveness of the applied signal processing algorithms for sensorless torque control are verified at low speed and heavy load.

Torque sensorless decentralized neuro-optimal control for modular and reconfigurable robots with uncertain environments

A technical challenge of addressing the decentralized optimal control problem for modular and reconfigurable robots (MRRs) during environmental contacts is associated with optimal compensation of the uncertain contact force without using force/torque sensors. In this paper, a decentralized control approach is presented for torque sensorless MRRs in contact with uncertain environment via an adaptive dynamic programming (ADP)-based neuro-optimal compensation strategy. The dynamic model of the MRRs is formulated based on a novel joint torque estimation method, which is deployed for each joint model, and the joint dynamic information is utilized effectively to design the feedback controllers, thus making the decentralized optimal control problem of the environmental contacted MRR systems be formulated as an optimal compensation issue of model uncertainty. By using the ADP method, a local online policy iteration algorithm is employed to solve the Hamilton–Jacobi–Bellman (HJB) equation with a modified cost function, which is approximated by constructing a critic neural network, and then the approximate optimal control policy can be derived. The asymptotic stability of the closed-loop MRR system is proved by using the Lyapunov theory. At last, simulations and experiments are performed to verify the effectiveness of the proposed method.