Data-driven command shaping for improved torque control accuracy of torsional dampers

The Y-Balance Test (YBT), especially the posteromedial (PM) reach direction (PM-YBT), is able to identify dynamic postural control deficits in those who have ankle instability. However, there still exists a need to understand how sensorimotor function at the ankle explains the performance during the PM-YBT. The purpose of this study was to determine whether the ability to accurately control eccentric ankle torque explained PM-YBT performance. It was hypothesized that eccentric dorsiflexion/plantarflexion torque control would be positively related to the maximum reach distance (MRD) of PM-YBT. Cross-sectional study. Twelve healthy subjects performed the PM-YBT, maximum voluntary isometric contractions (MVIC) for both dorsiflexion and plantarflexion muscle strength, and then the torque control testing of the ankle. The torque control testing provided a target torque level on a screen in front of the subject and passive rotations of the ankle joint in the sagittal plane at 10 deg/sec between plantarflexion to dorsiflexion. Subjects were then instructed to eccentrically contract the dorsiflexors and plantar flexors to generate torque while the ankle joint rotated. The accuracy of torque control during eccentric dorsiflexion and plantarflexion by calculating absolute errors, the area between the target torque and the produced torque were evaluated. Tibialis anterior and soleus muscle activities were simultaneously recorded during testing. A step-wise linear regression model was used to determine the best model predicted the MRD of the PM-YBT (PM-MRD). A step-wise linear regression developed a model explaining only eccentric dorsiflexion torque control predicted higher PM-MRD score (R2 = 44%, F1,10 = 7.94, β = -0.67, p = 0.02). The accuracy of torque control during eccentric dorsiflexion predicts better performance in the PM-YBT. 3b.

Torque traceability examination of calibration laboratories in Korea

High power applications with low switching frequencies as well as high speed applications with high fundamental frequencies operate at low switching-to-fundamental (S2F) frequency ratios. With low S2F frequency ratios, it is challenging to achieve high torque control accuracy and dynamic performance. This paper identifies control issues that yield performance degradation at low S2F frequency ratios, for traditional field oriented control (FOC) and for deadbeat-direct torque and flux control (DB-DTFC) induction machine drives. By eliminating the synchronous reference frame current regulation, DB-DTFC demonstrates advantages to achieve a more desirable torque control performance in low-S2F-ratio applications. Three progressively more accurate DB-DTFC torque models are compared in terms of torque control accuracy and computation time to FOC and standard high switching frequency DB-DTFC. A general guideline is proposed to select the most suitable model for DB-DTFC drives at an arbitrary S2F ratio for high power or high speed applications.

As an intelligent transmission device, the magnetorheological (MR) clutch cannot realize its accurate torque control because it is difficult to establish its accurate torque control mathematical model. This paper designs a squeeze shear MR clutch. In order to achieve accurate torque control of the MR clutch, this paper proposes a fuzzy proportional integral differential (PID) control strategy based on the optimization of the bee colony algorithm. Based on the mechanical transmission experiment platform of the MR clutch, the performance of the torque control of the MR clutch is experimentally studied by using the real-time operating system Phar Lap ETS built by LabVIEW real-time module, it is found that the fuzzy PID control strategy based on bee colony algorithm can not only improve the torque control accuracy of the MR clutch by 70% compared to traditional PID control strategies but also increase the response speed by more than 50%.

This paper proposes a simple method direct torque control (DTC) based on space vector pulse width modulation (SVPWM) of surface-mounted permanent-magnet synchronous motors (SPMSM). The proposed DTC method calculates the optimized voltage vector using the motor parameters and the analysis of the relationship between the stator flux, torque, and stator voltage to calculate the optimized voltage vector. Thus the overshoot does not occur and the fast and accurate torque control becomes possible. The voltage vector calculation is divided into three steps. First, the magnitude of the voltage vector is calculated using the reference torque. Second, even though the motor parameters are not precise, the accurate torque control can be achieved through the compensation of the voltage vector. Last, the angle of the voltage vector is calculated through the magnitude of the voltage vector and the stator flux error. The calculated voltage vector controls the motor instantly and accurately by operating the inverter through the DTC-SVPWM method. The effectiveness of the proposed DTC method is verified through simulation. The simulation result proves that new strategies provide low torque ripple and quick dynamic performance.

Deadbeat-direct torque and flux control (DB-DTFC) has demonstrated several technical advantages over classical hysteresis DTC and PI regulator based direct torque control (DTC) methods. These include fast torque control, low ripple, easily integrated dynamic loss minimization control, and one control law that uses the inherent Volt-sec. source properties of power electronics to enable operation over all operating conditions including voltage limits. DB-DTFC uses the fundamental machine model to form the inverse solution for Volt-sec selection at each switching period. Therefore, DB-DTFC is a model-based discrete time controller that relies on accurate machine parameter estimation to provide accurate dynamic torque control. In this paper, a new method for high frequency injection-based real-time self- and mutual inductance estimation is proposed and evaluated in both simulations and experiments. In this new method, the estimated inductances including cross-coupling inductance due to cross-saturation are then used to estimate the stator resistance and permanent magnet flux linkage. The stator flux linkage observer using the identified machine parameters, yields improved stator flux linkage estimates that enable precise torque calculation. Experimental evaluation of the HFI-based flux estimates on torque estimation and control accuracy is performed at an IPMSM drive test bench with torque transducer mounted.

Deadbeat-direct torque and flux control (DB-DTFC) is a direct torque control method that provides the fastest possible torque control, low ripple, easily integrated dynamic loss minimization control, and one control law that uses the inherent volt-second source properties of power electronics to enable operation over all operating conditions, including voltage limits. DB-DTFC is a model-based discrete time controller that relies on precise machine parameter, flux, and torque estimation to provide fast dynamic torque control. In this paper, a new method for high-frequency injection (HFI)-based self- and mutual incremental inductance estimation is proposed and evaluated in both simulations and experiments. In this new method, the estimated incremental inductances including cross-coupling inductance due to cross saturation are curve fitted offline and then used to calculate the apparent inductances. With the apparent inductances, the stator resistance and permanent-magnet flux linkage are estimated using recursive least squares method online. The stator flux linkage observer using the identified machine parameters yields improved stator flux linkage estimates that enable precise torque calculation. Experimental evaluation of the HFI-based flux estimates on torque estimation and control accuracy is performed at an interior permanent-magnet synchronous machine drive test bench with a torque transducer mounted.

This paper presents a comparative study of two popular torque control schemes which have evolved for PM synchronous motor drives in recent years. The current regulated torque control strategy which has been well established for a number of years and which exercises control in the rotor reference frame is compared with the direct torque control (DTC) scheme where current controllers followed by PWM or hysteresis comparators and dq transformations are not used. Accuracy of torque control in the face of variation of parameters of importance are discussed followed by the problems of implementation of either approaches. Experimental results comparing both strategies of torque control are presented.

A Flexible shaft-driven Remote and Torsionally Compliant Actuator (RTCA) for wearable robots

A new torque control method for DC-servo motors based on voltage control is proposed and investigated. Through analyzing the torque control system consisting of DC-servo motor, reduction gear and torque sensor, it is shown that torque control by voltage control is feasible. It is also possible to eliminate the static error of the output torque and the interference of the disturbance torque such as the friction at the reduction gear. According to the analysis, a prototype servo driver is developed. Since only the voltage control capability is needed for the servo driver, the volume and mass of the developed servo driver are around 30% of the conventional values. Through experiments using the developed servo driver, it is confirmed that accurate torque control is feasible by the proposed method.

A novel Lyapunov function-based direct torque controller for minimization of torque ripples in a switched reluctance motor (SRM) drive system is reported in this paper. SRM magnetization characteristics are highly nonlinear, where torque is a complex and coupled function of the phase currents and rotor position. The direct torque control (DTC) scheme avoids the complex process of torque-to-current conversion as required in indirect torque control scheme. The traditional DTC scheme uses a hysteresis-type torque controller and it leads to large amount of torque ripples when implemented digitally. The proposed controller is intended to take care of the nonlinear system dynamics of magnetic characteristics associated with accurate torque control using DTC scheme for the SRM drive system. In the Lyapunov function-based controller, the feedback gain is varied using a heuristic technique. The stability of the proposed controller is ensured by the direct method of Lyapunov. Experimental results for a 1-hp, 4-phase SRM are provided to demonstrate the efficacy of the proposed torque control scheme.

Highly accurate speed and torque controls are strongly required for induction motors especially at a low speed to maintain an accurately constant torque through a long time operation typically for rolling spread of steel sheet production. High accuracy of the 12 feedback control system is based on a condition of clear detection of 12 waveform at relatively higher speed region over around 500 rpm where the disturbing signal for 12 coming from 11 is relatively small due to the magnetic shielding effect of the shaft steel.In this paper, tried to introduce the finite impulse response digital low-pass filter (FIR digital low-pass filter) to effectively separated of 11 and 12 waveforms showing similar low frequencies and obtained an accurate torque control result through 83 min operation case with 40 rpm speed.

The traditional torque control method has the imbalance of fuel and air in the transient state due to the filling effect and hysteresis of the intake pipeline, leading the output torque accuracy and the response speed to decrease. Aiming at this problem, this paper proposes an accurate torque control algorithm based on transient intake air quantity observation. A dynamic manifold model is built based on physical mechanism. Based on this model, a transient intake air quantity observer is built to obtain the actual amount of intake air in transient work condition. On this basis, a model-based torque control architecture is constructed, the control method of model feedforward combined with ADRC feedback is used to control the output torque of the engine. Through bench test, it proves that the method can accurately estimate the instantaneous intake air quantity of the engine and effectively improve the control accuracy and transient response speed of the engine output torque.

Rehabilitation robots for active exercise requires compliant but consistent torque (or force) assistance (or imposition) while passive rehabilitation robots are programmed to execute certain movements for patients. This kind of torque assistance in the rehabilitation system can be provided by using SEA (Series Elastic Actuator). In this paper, low stiffness SEA and spring hysteresis compensation are proposed for the robust and accurate torque control of the rehabilitation robot. C-DSSAS (Compact Dual Spiral Spring Actuation System) is developed to implement the low stiffness SEA and a hysteresis compensation method is proposed for robust accurate torque control. Pros and cons of low stiffness SEAs are dealt with in order to explain validity of proposed application. In addition, proposed hysteresis compensation torque controller has backlash-based polynomial model and passivity-based control. Experiments of active exercise of knee were performed wearing the knee rehabilitation device using the C-DSSAS with hysteresis control. The experimental results demonstrate its improved performance of the robot in terms of the robustness and accuracy.

By analyzing the principle and method of the direct vector control torque control method for induction motor, an analysis method of the influence of motor parameter changes on the accuracy of motor electromagnetic torque control under steady-state conditions is proposed, and the application of four common flux observations is derived. In direct vector control, the error function of the electromagnetic torque is estimated. The influence of the change of induction motor parameters on the torque control accuracy is theoretically analyzed, and the simulation is verified by Simulink. The simulation proves that the method can correctly analyze the torque control accuracy under the condition of induction motor vector control without complicated calculations.