Showing papers on "Damping torque published in 1989"

High-performance direct torque control of an induction motor

Abstract: A novel direct torque control method for an induction motor is presented which is quite different from field-oriented control. Improving the torque response of a large-capacity induction motor using two sets of three-phase inverters and an open-data induction motor is of special concern. Instantaneous voltage vectors applied by an inverter have redundancy characteristics which provide some flexibility for selecting the inverter switching modes. By using this switching freedom, control is achieved according to the following priorities: (1) high-speed torque control; (2) regulation of the primary flux; (3) decreasing the zero phase sequence current; and (4) minimization of the inverter switching frequency. Simulations and experiments have been carried out to verify the feasibility of this priority control, accompanied by comparisons with another control scheme. Torque frequency-response corner frequencies above 2000 Hz have been experimentally measured, and time constants of 4 ms have been achieved for rotor-speed step responses from -500 to 500 r/min. The peak transient torque during the step change is about 20 times the rate torque. >

Torque estimator for switched reluctance machines

Abstract: Apparatus for estimating torque generated by a switched reluctance machine utilizes a ROM table look-up scheme to generate a torque estimate based upon phase current and rotor position information. Each ROM address is accessed by digitizing and then combining sensed phase current and rotor position signals. Knowledge of the instantaneous torque output enables closed-loop torque control including appropriate adjustments of phase currents to reduce or eliminate torque pulsations.

Method of operating a vibration attenuating system having semi-active damper means

Abstract: The system includes at least one semiactive damper whose switching between high damping and low damping states is at times delayed until the relative velocity across the damper is no greater than a preselected low magnitude, or until the energy stored by a resilient deformable system member is no greater than a predetermined magnitude, or until the first to occur of either of the foregoing events.

Passive computed torque algorithms for robots

Abstract: Computed torque algorithms are used to compensate for the changing dynamics of robot manipulators in order to ensure that a constant level of damping is maintained for all configurations. There are three significant problems with existing computed torque algorithms. First, they are nonpassive and, as shown, can lead to unstable behavior; second, they make poor use of actuator capability; and third, they cannot be used to maintain a constant end-effector stiffness for force control tasks. A new class of passive computed torque controller which have guaranteed stability properties, utilize actuators effectively, and maintain constant end-effector stiffness is introduced. Network models are used to motivate and illustrate the approach. >

Design and Development of Torque- Controlled Joints

Abstract: This paper discusses the effect of basic manipulator characteristics upon the implementation of high performance joint torque control. Two manipulators with very different characteristics (high and low gear ratios) are used in this analysis: The PUMA 560 manipulator and ARTISAN, a ten degree-of-freedom manipulator currently under development at Stanford. The experimental results obtained with a prototype link of ARTISAN are presented and compared to those previously obtained with the PUMA. This paper also describes conceptually a new type of torque sensor, developed during the course of this project. With this new sensor, using inductive contactless transducers, torques are evaluated by distance measurements of deflections in the sensor's structure. The new sensor provides a substantial increase in accuracy over conventional strain gauge sensors, achieves higher mechanical robustness, and presents lower sensitivity to electrical noise.

Semi-active damper valve means and method

Abstract: An improved method and means for control and accomplishment of semi-damper assembly transition between high damping and low damping states is provided which takes advantage of the available inherent dynamic fluid pressure forces produced by the condition of motion between supported and supporting members. Deferral or delay of damper state transitions to avoid force discontinuities or system noise is accomplished mechanically, or automatically internal to the structure of the adjustable valve assembly. A voice coil actuated valve slider is operable within the piston of the damper assembly to modulate the damping coefficient in conjunction with check valves. The delay of damper state transition from high to low damping is accomplished independent of the particular control policy utilized until the fluid pressure differential across the valve slide is a preselected low value. Commanded valve switching and motion condition sensing requirements are also minimized by the reversible check valves. Damper state transitions normally required based on a sign change in relative velocity are accomplished without commanded slider movement by the check which are fluid pressure actuated according to the direction of fluid flow through the damper.

Method and apparatus for sensing and damping vibration

Abstract: A shape memory alloy used for both sensing and damping vibration of a structure. In one embodiment, a flat bar (12) is mounted from one end on its edge so that its other end vibrates from side-to-side at its natural resonant frequency. A vibration damping wire (30) extending longitudinally along one surface of the bar is mounted under tension between spaced apart standoffs (32); a sense wire (42) is similarly mounted along the opposite surface of the bar. The vibration damping wire and sense wire comprise a nickel-titanium (Nitinol) alloy, having a relatively high specific damping coefficient. Absorption of kinetic energy by the vibration damping wire when it is stretched by deflection of the bar greatly reduces the time required to passively damp vibration of the bar, compared to its undamped resonant time. the vibration damping wire is heated above a transition temperature by an electrical current pulse while relaxed to restore it to its unstretched length. The sense wire changes resistance in proportion to stress applied to the wire so that a voltage drop across the sense wire corresponds to the vibrational displacement of the bar. The voltage drop signal is used to control application of the current pulse in synchronization with the vibratory motion of the bar. To actively damp vibration of the bar, the pulse of electrical current is applied to heat the Nitinol alloy above its transition temperature so that it resumes a foreshortened memory shape as the bar's vibratory deflection tries to stretch the vibration damping wire. The vibration damping wire thus applies a force to the bar in opposition to its vibration. Other embodiments include a cylinder (52) and a vibration damped strut assembly (80). In these latter two embodiments, vibration damping wires and sense wires are disposed internally within the structure. A digital control (110) or analog vibration damping control (200) controls the application of current pulses to heat a selected vibration damping wire above the transition temperature in phase with the signal produced by the sensor wire.

Torque hold system and method

Abstract: Hydraulic tongs, used to screw oilfield tubulars together, are equipped with torque control means which enable the tongs to rotate the tubulars and then gradually apply torque until a preselected torque value is reached, hold the torque at this value a desired period of time and then release the torque. In one form of the invention, a tong control restricts the power of the tong motor to enable low torque rotation while limiting the maximum torque which can be produced by the tong motor. A hydraulic cylinder placed in the tongs' restraining line is controlled to shorten, hold or extend the line. When the line is shortened, the tongs are pulled in a direction which increases the torque to a value above the maximum torque produced by the tong motor. The system allows heavy, powerful tongs to be used to accurately apply and hold a wide variety of selected torque values.

Torque measuring device

Abstract: A device for measuring torque in a shaft without contacting the latter. A torque transmitting shaft is formed with at least one detecting magnetically anisotropic region inclined to form an angle with respect to the axis of rotation of this shaft. A detecting coil is disposed on the periphery of the detecting magnetically anisotropic region. When the detecting voltage for the detecting coil changes owing to temperature changes and time-dependent changes, the changes in the detection sensitivity and in the zero point take place, leading to errors during torque measurement. Correct measured values can be obtained by having a device for correcting such changes in sensitivity and zero point.

Damping characteristics variable hydraulic shock absorber for automotive suspension system with vehicular attitude suppressing capability

Abstract: A hydraulic shock absorber is provided a capability of quick response in such an extent that harder damping characteristics is provided during bounding stroke in each vibration cycle and softer damping characteristics is provided during rebounding stoke in each vibration cycle. The hydraulic shock absorber is controlled the damping characteristics for damping road shock by switching damping characteristics between harder damping characteristics and softer damping characteristics during normal mode operation. On the other hand, in attitude change suppression mode, suspension characteristics for suppressing vehicular body attitude change irrespective of the vibration mode.

Multiaxis robot controller having workpoint torque control

Abstract: Workpoint torque control is employed in an electron multiaxis robot controller. Robot axis torque is determined from axis motor current feedback. Axis torque requests are based on torque command and torque feedback in an axis torque control mode or on the basis of position, velocity and torque commands and position, velocity and torque feedback in a combined position/torque control mode, or an indirect torque control mode.

Active control system and method for reducing engine noise and vibration

Abstract: Noise and vibration in a structure is reduced through application to the structure of an oscillatory torque. An electromechanical energy converter provides the oscillatory torque when the input signal to the electromechanical energy converter has a frequency and harmonics thereof required to counteract the noise and vibration desired to be attenuated.

Torque control system for engine performance test machine for internal combustion engines

Abstract: A torque control system for an engine performance test machine for internal combustion engines comprises an oscillating type electric dynamometer including a rotor and an oscillating member being oscillatably supported around said rotor and a connecting device for interconnecting the rotor shaft and the rotating member of the engine. The torque control system also includes a load cell for monitoring oscillating torque of the oscillating member, means for generating a first torque occurring at the rotor, means for generating a second torque occurring at the rotating member. The torque control system also includes means for generating a detection signal representative of the sum of said oscillating torque, and the first and second torques, and a controller for adjusting the torque generated by the engine in response to the detection signal.

Apparatus and method for controlling electric car

Abstract: A PWM (pulse width modulation) inverter (5) generating an ac output having a variable voltage and a variable frequency supplies ac power to linear induction motors (61 to 64) An electric car supported by wheels (8) is driven by a driving torque produced by the linear induction motors While the electric car is running, the motor torque varies due to various factors among which a variation of the air gap length is representative The power factor cos φ of the PWM inverter is detected to calculate the motor torque, and the output voltage of the PWM inverter is regulated or mechanical brakes (9) are controlled so as to compensate the torque variation Thus, the variation of the air gap length, which is representative of the factors giving rise to torque variations and which has been difficult to be detected, can be reliably detected to permit torque control according to the torque variation of the linear induction motors (61 to 64)

Servo control apparatus

Abstract: A servo control apparatus which generates a torque command based on a difference between an instructed speed and a real speed in order to control the speed of the servo motor based on the torque command. Provision is made of a condition observation unit (50) which converges into zero the deviation between the real speed of the motor and an estimated speed and the deviation between the disturbance torque and the estimated disturbance torque. The estimated disturbance torque is input to a high-pass filter (70) to generate a correction torque command, the torque is corrected through a torque command correction unit (15), and the corrected torque command is input to the servo motor (18) to control the speed.

Control system for torque converter of automatic transmission

Abstract: A control system for a torque converter includes a lock-up clutch provided in a torque converter for connecting an input member and an output member of the torque converter directly. An engaging and disengaging hydraulic device controls an engaging and disengaging action of the lock-up clutch. A shift valve provided with a first and second spools in series controls introduction of a driving hydraulic pressure into the hydraulic device. The first spool of the shift valve is subjected to a first hydraulic pressure at one end, while the second spool is subjected to a second hydraulic pressure at the other end. The first and second spools are subjected to a third hydraulic pressure therebetween. The control system further includes a first control device for controlling the first hydraulic pressure, a second control device for controlling the second hydraulic pressure, an adjusting valve for adjusting the driving hydraulic pressure introduced into the engaging or disengaging hydraulic device, and a third control device for controlling a hydraulic pressure for controlling the adjusting valve. Converter, lock-up and slip conditions of the torque converter can be selectively established by switching shift positions of the single shift valve.

Analysis of torque ripple in electronically commutated permanent magnet machines and minimization methods

Abstract: The authors deal with permanent magnet machines with rectangular induction and current waveforms. In order to minimize the machine torque ripple, the evolution of the torque curves of the different windings supplied with constant current in function of the position of the rotor, must have a trapezoidal shape comprising a plateau with the correct width. They must be correctly juxtaposed by an adequate choice of the supply sequences. Moreover, in order to get the most out of the torque, an optimal use of the air-gap must be made by making the largest number of conductors work simultaneously. The influence of different parameters on the constant current torque curve shape are examined. The different ways of combining these torque curves are analysed so as to come to the best use of the air-gap and minimize the resulting torque ripple at the same time. >

Torsional oscillations of unequally-loaded parallel identical turbine-generators

Abstract: This paper provides a detailed analytical investigation of the torsional phenomenon of closely coupled parallel identical T-G sets, under unequal loading conditions. The impact of important factors, i.e., 1) load difference of generators, 2) mechanical damping torque components and 3) series capacitor compensation level on the torsional modes of unequally loaded parallel T-G set, are examined. The studies are conducted on a system composed of two parallel identical T-G sets. An eigenvalue method is used for the studies and the analytical results are verified by detailed digital computer simulation of the system, using the EMTP. The T-G sets also represented by the so called EGM, and whenever applicable, the study results are compared with those obtained from the EGM. The studies indicate that the corresponding torsional modes of the parallel T-G sets under unequal loading conditions, are not in-phase. The phase-deviation depends on: 1) the load-difference of the generators and 2) the mechanical damping torque components. Among the mechanical damping coefficients, i.e., mutual-damping coefficient, absolute-speed self-damping coefficient and speed-deviation, self-damping coefficient, the first two are constants and the third one is load dependent. The mechanical damping torque components corresponding to the speed-deviation self-damping coefficients have a noticeable impact on the phase-deviation. This paper also reports the results of an investigation in which an SVC system is used to mitigate the torsional oscillatory modes of the unequally loaded T-G sets.

Effect of excitation systems and of power system stabilisers on synchronous generator damping and synchronising torques

Abstract: The synchronising and damping torque coefficients in the range of the electromechanical oscillation frequencies provide a measure of the generators' contribution towards power-system stability under small deviations, and may be taken as stability indices even for multimachine systems, although their interpretation is rather complex in this case. The paper presents the development of an expression to calculate the electromagnetic torque for small deviations around an operating point, as produced by a synchronous generator connected to an infinite busbar through an impedance; it explicitly includes the effects of its automatic voltage regulator (AVR) and of the additional stabiliser signal derived from the rotor speed. In addition, numerical results from an evaluation of the damping and synchronising torque coefficients obtained from the expression are presented for a given generator. This is done in such a way as to emphasise the effect of a static-excitation system on the deterioration of the damping torque, and the effect of the stabiliser signal leading to an increase of the synchronous generators dynamic stability. The paper also discusses the effects of the presence of the damper windings, and of the system operating conditions and reactance variations.

Method and device for reducing torque loading on a system driven by an electric motor

Abstract: A method for reducing effects of torque fluctuations on a system driven by an electric motor and producing cyclically occurring, rotational speed-dependent load-torque fluctuations includes counteracting changes in load torque by effecting oppositely directed changes in drive torque so as to maintain the load torque at an approximately constant value.

Controllable vibration damper

Abstract: A controllable vibration damper for automotive vehicles is disclosed having a damping piston which is axially slidably and sealedly guided in a damping tube, and which subdivides the damping tube filled with a damping medium into two working chambers. The connection between the two working chambers is provided with at least one non-regulated first valve and at least one controllable second valve, which valves are arranged acting hydraulically in parallel in respect to one another. In order to be able to regulate the effective damping force continuously in wide ranges, for the adjustment of damping hardness, the controllable valve will periodically open and close in rapid sequence in dependence upon pulsed control signals.

Coordinate measuring machine with vibration damper

Abstract: A vibration damper disposed in a gantry-type coordinate measuring machine. The vibration damper includes a block having a substantial mass suspended from the moving gantry-type structure by highly energy absorbent pads having a low rebound resilience. The vibration damper is preferably spaced from the point at which the gantry-type structure is coupled to the drive therefor.

Torque control system and method

Abstract: An air tool torque control system includes a controller operative to independently control two air tools with continuous programmed adjustment of the torque shut off point for each tool after each fastener joint is made. The torque specification is measured for each fastener joint made, is verified as being within an acceptable torque range, is compared to the set point of that torque specification range to determine the variation therebetween, and is then adjusted toward the mid point by the applicable correction factor for the variation determined to continuously compensate for variations in joint rate, line pressure and/or tool output. To enhance the effectiveness of the system, fast acting solenoid valves utilizing line pressure to assist in valve closure may be included to improve shut off control. Torque select devices may also be included at the assembly station to allow selective switching of each tool to preprogrammed discrete torque ranges for specific fastener applications performed at that station.

Method and apparatus for checking torque sensor in electric power steering system for vehicle

Abstract: A method for detecting abnormal condition of a torque sensor in an electric power steering system in which a power of an electric motor assisting steering operation of a vehicle is supplied in response to a torque signal generated from the torque sensor, the method comprising the steps of detecting a condition where the torque signal generated from the torque sensor is substantially equal to zero, detecting another condition wherein the rate of changing steering angle is larger than a predetermined value, while the steering angle is held in an increasing state, and further detecting that the above detected conditions last more than a predetermined period.

Continuously variable transmission provided with a torque converter

Abstract: A continuously variable transmission (3, 4, 5, 6, 7, 8, 9) is provided with a torque converter (2) having an ingoing shaft (1), whereby the torque converter has such torque converting factors at various speeds of the ingoing shaft that the torque characteristic of the torque converter approximates the characteristic of the maximum torque to be transmitted by means of the transmission and the control system for a substantial part of the speed range. This results in an increased torque at low speeds of the ingoing shaft, especially at driving off in a motor vehicle. Furthermore a loss of power is reduced because an overdimensioning of the control system which controls the pressure in control cylinders (18, 19) of the transmission is no longer needed.

Automatic tensioning device

Abstract: An automatic tensioning device for drive belts is equipped with a friction damper with low damping action against vibrations transmitted by the drive belt. A hydraulic shock damper has with high damping action is provided for large surge pulses. Preferably, the hydraulic shock damper an idle stroke in which the friction damper is active.

Torsional vibration damper with liquid damping

Abstract: The invention relates to a torsional vibration damper with hydraulic damping, in which spring plates which assume the task of power transmission to the helical springs are used as displacement bodies.

Controller for brushless synchronous motor

Abstract: PURPOSE: To improve the linearity of a required torque and output torque by providing a cogging torque compensator for compensating a cogging torque being the variation of a generated torque and not depending on the magnitude of the generated torque and a torque constant compensator for compensating a part depending on the magnitude of the generated torque. CONSTITUTION: In the controller of a brushless synchronous motor 1, a required torque T* from a host controller 6 is subtracted by cogging torque compensating data Tcog(θ) not depending on the magnitude of a generated torque read from a cogging torque compensator 4 by means of a rotation angle θ from a position transducer 2 as a parameter. The subtraction-compensated required torque T* is converted into a current command i f * multiplied by the inverse number of a torque constant read from a torque constant compensator 5 by means of the rotation angle θ from the position transducer 2 as a parameter. The linearity of the obtained generated torque and required torque T* is considerably improved by the current command iT*. COPYRIGHT: (C)1991,JPO&Japio

Control cable system with device for reducing vibration

Abstract: A control cable system with a device for damping vibration comprising a control cable an end of which is connected to a vibration source, a vibration member connected to another end of the control cable and a dynamic damper The dynamic damper is attached on an element of the control cable and is tuned to have a special frequency characteristic That is, the tuned damper vibrates when it receives a vibration having a frequency in a range including a plurality of resonance frequencies of the vibration member, and the damper resonates in response to a special resonance frequency in the range

A damping circuit for chopper driven bifilar hybrid step motors

Abstract: The major disadvantage of a chopper-driven step motor is its poor damping characteristics. The causes of poor damping are investigated, and the effects of various motor parameters on damping are discussed. A simple circuit to improve the damping response of the step motor is proposed. Results obtained from computer simulations are presented. >