Abstract: To appropriately detect overload which may break a motor or deform a body and reduce the overload in the motor. The DC component of a load torque is derived from the sum of absolute values of a torque applied to a link connected to the output shaft of a motor and the generated torque of the motor, and it is determined that overload has been applied when the DC component exceeds a first threshold value for a prescribed period of time or longer. In addition, considering such a characteristic that the variation of energy applied to the output shaft of a motor is in proportion to a product of the torque and the angular velocity of the motor, the AC component of the load torque is detected based on the variation of energy, and it is predicted that overload will be applied when the AC component exceeds a second threshold value.

Abstract: To appropriately detect overload which may break a motor or deform a body and reduce the overload in the motor. The DC component of a load torque is derived from the sum of absolute values of a torque applied to a link connected to the output shaft of a motor and the generated torque of the motor, and it is determined that overload has been applied when the DC component exceeds a first threshold value for a prescribed period of time or longer. In addition, considering such a characteristic that the variation of energy applied to the output shaft of a motor is in proportion to a product of the torque and the angular velocity of the motor, the AC component of the load torque is detected based on the variation of energy, and it is predicted that overload will be applied when the AC component exceeds a second threshold value.

Abstract: A device for active vibration damping dampens the structural resonance of an elevator car frame with a car body through measurement of the deformation of the frame. Under elastic deformation, a safety plank and a crosshead of the frame move parallel and relative to each other and two acceleration sensors aligned vertically (in the “z” direction) capture the movement. From the difference between the sensor signals, the “y” rotation of the safety plank and the crosshead is determined. The rotation and the signals from acceleration sensors on the frame are used to determine the shear movement of the frame.

Abstract: To appropriately detect overload which may break a motor or deform a body and reduce the overload in the motor. The DC component of a load torque is derived from the sum of absolute values of a torque applied to a link connected to the output shaft of a motor and the generated torque of the motor, and it is determined that overload has been applied when the DC component exceeds a first threshold value for a prescribed period of time or longer. In addition, considering such a characteristic that the variation of energy applied to the output shaft of a motor is in proportion to a product of the torque and the angular velocity of the motor, the AC component of the load torque is detected based on the variation of energy, and it is predicted that overload will be applied when the AC component exceeds a second threshold value.

Abstract: To appropriately detect overload which may break a motor or deform a body and reduce the overload in the motor. The DC component of a load torque is derived from the sum of absolute values of a torque applied to a link connected to the output shaft of a motor and the generated torque of the motor, and it is determined that overload has been applied when the DC component exceeds a first threshold value for a prescribed period of time or longer. In addition, considering such a characteristic that the variation of energy applied to the output shaft of a motor is in proportion to a product of the torque and the angular velocity of the motor, the AC component of the load torque is detected based on the variation of energy, and it is predicted that overload will be applied when the AC component exceeds a second threshold value.

Abstract: To eliminate unwanted vibrations caused by synchronous disturbances, such as synchronous disturbances caused by an imbalance, for example, the invention proposes a compensation device for closed loop compensation of a synchronous disturbance in a rotating machine comprising a rotor (64) magnetically suspended by at least one radial magnetic bearing (63) comprising electromagnets (631, 632) driven by amplifiers (61, 62), a radial detector device (633, 634) for sensing the axial position of the rotor, and a closed loop servocontrol circuit connected to said detector device and to said electromagnets and comprising a control circuit (5) for controlling the energization of the electromagnets that supplies a control signal (u) to said amplifiers in response to signals supplied by the detector device to maintain the rotor in a predetermined axial position. The compensation device comprises means (100; 200; 300) for generating a signal for compensating the synchronous disturbance.

Abstract: Load cycle oscillations in the drive train of a motor vehicle are reduced by detecting a change in available torque in the drive train, determining the period of a load cycle oscillation, and, at the commencement of the available torque change, applying at least one additional torque pulse, which causes an oscillation in phase opposition to the load cycle oscillation and which lasts half the period of the load cycle oscillation.

Abstract: A lithographic projection apparatus in which a reaction force is generated between a balance mass and a substrate table. The balance mass is elastically coupled to the base frame with a suspension eigenfrequency of between 0.3 and 10 Hz.

Abstract: A driving apparatus which drives an object along a guide surface in X and Y directions. The apparatus includes a first actuator which drives the object in the X direction, a second actuator which drives the object in the Y direction, and a controller which controls the first and second actuators. The first and second actuators each have a reaction force counter which moves upon receipt of a reaction force generated in driving the object. In moving the object standing at a first position to a second position and stopping the object, the controller controls the first and second actuators such that acceleration periods of the two coincide and deceleration periods of the two coincide. Also, the object moves on a straight line connecting the first position and the second position.

Abstract: A magnetic bearing system allows a movable body to be positioned to a point of substantial equilibrium in an axial direction after a system shutdown. A sensor measures the axial position of the movable body to produce an displacement output. That output is then adjusted to account for a sensor offset. The adjustment is stored and can be used to position the movable body during regular operation of the system or when the system reboots or restarts. The adjusted displacement output is converted into a force for positioning the movable body. The movable body may be a rotor in a heart pump apparatus.

Abstract: In servomechanisms, like for example used in disk drives, disturbances, for example, friction, shock and vibration, prevent the system positioning accuracy from further improvement. These disturbances occur in a relatively low-frequency range compared to the electrical dynamics. In the present invention, an acceleration feedback control loop using a frequency-separated acceleration soft sensor (350) replaces the conventionally used current control loop in the low frequency range, where the disturbances occur, so as to attenuate the influence of the disturbances enclosed in the loop. The current feedback continues to manage the electrical dynamics in the high-frequency range. Estimating the required acceleration signal by a soft sensor (350) eliminates the need for physical accelerometers, which reduce system reliability and increase system cost.

Abstract: In a positional control device for controlling a position of a controlled object using a motor, when generating a torque command value ?c which serves as the command value for the servo motor of the controlled object system (112), a friction compensation value for use when the controlled object initiates a movement is calculated based on a velocity command value V and a torque command value ?c determined according to a positional command value Xo supplied from a superordinate device. More specifically, an initial friction compensation calculating section calculates a torque compensation amount Vsfc1 corresponding to a difference between torque being generated during the standstill state and torque required by the controlled object to initiate the movement, and a torque compensation amount Vsfc2 to an amount of change in friction that occurs during a transition from static friction to kinetic friction in a period immediately before and after initiation of the movement.

Abstract: A motion controller for maintaining a controlled system on a switching hyperplane regardless of the magnitude of disturbance. The motion controller includes a target position generator, a sliding mode controller, a disturbance observer and a state observer. The target observer generates a target position to the sliding mode controller based on position and velocity data. The state observer estimates the state of the controlled system and provides the state to the sliding mode controller. And, the disturbance observer provides an estimated disturbance to the sliding mode control. The sliding mode controller generates a control input to the controlled system with the nonlinear component set to equal the negative estimated disturbance and the linear component based on the estimated state and target position.

Abstract: A motor comprises: coil on/off switching devices for switching between an on-state wherein current is supplied to the coils, and a first off-state wherein the coil terminals are open-circuited or a second off-state wherein the coil terminals are short-circuited; and a coil current control device for controlling switching operations of the coil on/off switching devices according to commands input to the motor. In the event that motor movement with great mechanical compliance is required, the ratio of the period of the first off-state is increased, and on the other hand, in the event that motor movement with great viscosity resistance is required, the ratio of the period of the second off-state is increased. This solves the problems of torque loss and cogging during a period wherein no current is applied to the coil.

Abstract: A system and method for controlling an active magnetic bearing assembly by varying the system control laws in a continuous non-linear fashion as a function of rotor rotational speed. The system control law variation is carried out in a continuous and optimal manner over the operating speed range of the rotor, and is not computationally intensive.

Abstract: The invention relates to a numerical controlling unit that includes: a instructing part that provides a command acceleration for a servomotor, a parameter storing part that stores a threshold parameter about a load of the servomotor, and a load measuring part that measures the load of the servomotor. The load measured by the load measuring part and the threshold parameter are compared by a load comparing part, and an acceleration adjusting part changes the command acceleration for the servomotor based on a result compared by the load comparing part. A controlling part controls the servomotor based on the changed command acceleration. According to the invention, the command acceleration for the servomotor is suitably changed based on the result of comparing the load measured by the load measuring part and the threshold parameter. Thus, it can be prevented that the servomotor is subjected to an overload while using the maximum performance in feeding a work piece.

Abstract: The servo control method operates a set value of a first-order lag time constant of a feedback compensation by both a detected mechanical position value and a transfer function corresponding to a change of an angular velocity about each axis under a multiple-axes simultaneous control. Further, the servo control method sets a feedforward amount so that the transfer function about the each axis is the same.

Abstract: A stage apparatus is disclosed, which includes first and second movable members movable in directions parallel to a reference plane, a first actuator for generating a force between the first movable member and the second movable member, a second actuator for generating a force between a structure defining the reference plane and the second movable member. A first control system controls the position of the first movable member, using the first actuator, and a second control system controls the position of the second movable member, using the second actuator in synchronization with the control of the first control system.

Abstract: An energy absorbing filter for reducing mechanical oscillations in motor is disclosed. The energy absorbing filter places a virtual shunt across the motor windings so as to dissipate mechanical vibrations as resistive losses. This is accomplished by the placing of a large capacitance in parallel with the windings. The impedance of the filter and the windings combined is purely resistive. The motor may be any kind of motor including a 2-, 3-, or 5-phase hybrid step motor. The filter may be realized as an analog or digital filter, or may be a hybrid of the two. Additionally, the filter may be realized through hardware or through software in the form of a computer program.

Abstract: A servo controller capable of driving a single movable member by two motors with high loop-gain setting to obtain a quick response. A servo controller includes two position controllers associated with respective motors and a damping controller. Each of the position controllers has a position control section to output a velocity command based on an identical position command from a host controller and a position feedback value from an associated position detector, a velocity control section to output a current command based on the velocity command and a velocity feedback value from an associated velocity detector, and a current control section to output a voltage command based on the current command and a current feedback value from an associated current detector. The damping controller outputs a current command correction value for compensating an interference between the two motors based on the velocity feedback values from the velocity detectors for the two motors.

Abstract: An oscillation isolator for supporting an oscillation isolation platform on a pedestal includes an active oscillation isolator having a displacement generating type actuator to reduce oscillation of the platform and a displacement adjuster provided between the active oscillation isolator and the platform or the pedestal for adjusting relative displacement between the active oscillation isolator and the platform or the pedestal. The displacement adjuster has a rigidity higher than that of the active oscillation isolator and is dynamically located in series between the active oscillation isolator and the platform or the pedestal.

Abstract: The invention relates to a numerical controlling unit that includes: a instructing part that provides a command acceleration for a servomotor, a parameter storing part that stores a threshold parameter about a load of the servomotor, and a load measuring part that measures the load of the servomotor. The load measured by the load measuring part and the threshold parameter are compared by a load comparing part, and an acceleration adjusting part changes the command acceleration for the servomotor based on a result compared by the load comparing part. A controlling part controls the servomotor based on the changed command acceleration. According to the invention, the command acceleration for the servomotor is suitably changed based on the result of comparing the load measured by the load measuring part and the threshold parameter. Thus, it can be prevented that the servomotor is subjected to an overload while using the maximum performance in feeding a work piece.

Abstract: When a drive unit which drives a reticle stage accelerates or decelerates it, the reaction experienced by this drive unit is discharged to a floor FD via an actuator, an attached member, and a reaction frame. Vibration generated in the reaction frame at this time is detected by an acceleration sensor. A vibration cancellation control section determines a direction and thrust for driving a movable section to which a weight is fixed in order to quell vibration of the reaction frame detected by the acceleration sensor, and emits a control signal to a driver.

Abstract: A control system for determining a control function for a control device on the basis of a transfer function of an object to be controlled and for adjusting an operation quantity of an object to be controlled in accordance with the determined control operation function, wherein an control function of a first control device is determined so that a closed-loop transfer function of a control system including the object to be controlled and the first control device coincides with a predetermined first transfer function, an control function of a second control device is determined, in a closed loop control system including the control system and the first control device, so that a transfer function from a disturbance applied to the object to be controlled to a state variable of a point at which the disturbance is applied to the object to be controlled, and a sum signal indicative of a sum of outputs of the first and second control devices is used as an operation quantity of the object to be controlled.

Abstract: A magnetic bearing wherein a stator is magnetically interacted with a rotor and is movable in response to feed-back of rotor position to thereby use the magnetic interaction between the stator and rotor to effect movement of the rotor toward a predetermined rotor position for bearingly controlling the rotor position. The bearing may be a radial or thrust bearing.

Abstract: A motor controller includes a summing circuit (186) for summing a motor current command signal (i.sub.rcmd) with a motor current feedback signal (i.sub.s) and for providing an error current command signal (.DELTA.i.sub.cmd) having a value functionally related to the difference between the motor current command signal and the motor current feedback signal. A notch filter (200) filters the error current command signal and provides a filtered current command signal. The notch filter (200) is adapted to notch out frequencies from the error current command signal about the resonant frequency of a motor (28). A drive circuit (120, 204) energizes the motor (28) in response to the filtered current command signal. A motor current sensor (97) is used for sensing motor current and providing the motor current feedback signal (i.sub.s).

Abstract: A control system stabilizes the flexible body bending modes of a space, airborne, or ground-based system, while providing angular position control of an oscillating mass connected to a counter-oscillating counterbalance. The actuating mechanism uses two drive motors to exert torques on the mass and counterbalance, respectively, under the control of a feedback controller. The controller has a first control channel generating a first torque command signal for the first drive based on the angular position of the mass, and a second control channel generating a second torque command signal for the second drive based on the angular position of the counterbalance and a torque cross-feed signal from the first control channel. The second control channel includes a notch filter for removing input frequencies in a predetermined bandwidth about the frequency of the first torque command signal.

Abstract: An apparatus and method for reducing vibrational noise generated by the operation of a machine. The machine includes an electric motor that is driven by a drive current generated by a power source. The vibrational noise generated by the operation of the machine induces a waveform in the drive current. An input device monitors the waveform of the drive current and quantifies the induced waveform. A signal processor translates the quantified waveform into a control waveform. A control device adds the control waveform to the drive current, thereby reducing the vibrational noise generated by the machine.

Abstract: A circuit for controlling a servomotor while minimizing a steady-state velocity error being associated with the servomotor. A velocity transducer is coupled to the servomotor to provide a first signal representing an angular velocity of a servomotor shaft. A comparator receives as input the first signal and a second signal representing a desired angular velocity of the servomotor shaft. The comparator produces a comparator output signal representing the steady-state velocity error as defined by a difference between the angular velocity of a servomotor shaft and the desired angular velocity of the servomotor shaft. Means are provided for deriving a value of a current flowing through the servomotor and for producing a third signal representing that current. The third signal represents a frictional torque applied to the servomotor shaft. An adder receives as input the comparator output signal and the third signal.

Abstract: It is an object of this invention to attain reliable starting characteristics and stable rotation performance of a motor in a motor of a phase synchronization driving type.

Abstract: A device and a method of controlling the vibrations of a two-inertial resonant system. The method includes the steps of detecting the electrical torque and the speed of a motor to evaluate the speed and the disturbance torque of a load, and a torsional torque generated by a difference in position between the driving means and the load; evaluating the acceleration of the load from the evaluated disturbance torque of the load and the torsional torque, and conducting a PI control by using the difference between the evaluated speed of the load and a reference speed of the load; and controlling the motor by using the difference between the evaluated acceleration of the load and the reference speed of the PI-controlled load.

Abstract: In many uses of electrical motors, the interaction of a tool being powered, e.g., a milling machine, and the workpiece being worked on by the motor induces mechanical vibrations which adversely affect the functioning of the tool as well as inducing wear producing vibrations in the motor rotor shaft. Damping of such vibrations is achieved by deliberately inducing internal unbalanced forces on the motor rotor shaft for counteracting the externally induced vibrations. Such internal unbalanced forces are produced by the use of additional currents in the main stator coils for generating additional, unbalanced force generating magnetic fields. A mathematical analysis of the process is provided.

Abstract: In a stage for supporting an article, e.g. for a microlithographic system, the stage rides on a base and is driven in two orthogonal directions on the base along magnetic drive tracks by several drive coils riding in the drive tracks. Each drive coil, rather than being rigidly mounted to the stage, instead is connected to the stage by a tapered connecting member (beam). One end of each beam is connected to the stage by a double flexure assembly. The other end of each beam is connected to the drive coil by a similar double flexure assembly. Each double flexure assembly includes two orthogonal flexible members (stainless steel strips). Thus vibrations are reduced by use of this multiple flexible joints.

Abstract: A stage feeding device has a movable guide which is guided on a reference surface of a platen to be movable in the Y-direction, a Y-linear motor for moving the movable guide in the Y-direction, a movable stage which is supported by the movable guide to be movable in the X-direction, and carries an object, and an X-linear motor for moving the movable stage in the X-direction. The stator of the X-linear motor is supported by a second stationary guide to be movable in only the Y-direction independently of the movable guide, and is moved in the Y-direction by a driving mechanism. The stator of the Y-linear motor and the second stationary guide are fixed to the base, and mount members for removing vibrations are arranged between the base and the platen.

Abstract: A servomotor controlling method and apparatus for use in two inertial systems in which the servomotor and a load are mutually connected by an elastic connection element is provided. A compensation torque value for suppressing oscillation is obtained on the basis of a torque command value for the servomotor and a motor output velocity. The compensation torque value is reflected on the torque command value to then be provided to the servomotor. Accordingly, a resilient torsional torque generated between a driving inertial system and a driven inertial system is properly corrected to thereby suppress oscillation and improve system stability.

Abstract: The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion.

Abstract: Dimpling of a workpiece by rebounding of a magnetic repulsion punch mechanism, when operated at high punching rates, is avoided by application of a damping pulse at a point at or subsequent to a mid-point of a return stroke of the punch from the workpiece and preferably within the last 10% of the return stroke. This damping pulse is preferably a fraction of the pulse width and of approximately the same amplitude as a driving pulse applying kinetic energy to the punch for causing punching of the workpiece. At high punching rates the kinetic energy of the return portion of a punching stroke is substantially determined by elastic rebounding of the punch from a guide bushing. The removal of kinetic energy during the return portion of the stroke allows the return of the punch to a position close to a rest position during a very short interval with small overshoot under control of mechanical damping.

Abstract: For the suppression of radio frequency emissions from an electrical drive comprising an electric motor supplied with electrical power via an electronic controller having a high speed switching device which generates high frequency energy, an electrical screen is provided to receive the radio frequency energy and is connected back to the input side of the high speed switching device.

Abstract: An apparatus for electromagnetically and rotationally vibrating a rotary body that is supported by bearings. The apparatus comprises a ring-shaped magnet bipolarly magnetized and mounted coaxially on a shaft of the rotary body, a ring-shaped stator having a coil and adapted to generate a rotating magnetic field by controlling an electric current supplied to the coil, and a frequency variable vibration power source adapted to supply alternating electric power to the coil in the stator. The distance between a location of a magnetic pole in the stator and an axis of the shaft is different than the distance between a location of a magnetic pole in the magnet and the axis of the shaft. The magnet and the stator are disposed so as to be adjacent to each other. Thus a rotational exciting force is applied to the rotary body by an interaction of the rotating magnet field generated by the stator with the magnet.

Abstract: A method for the compensation of periodic shaking forces in an AC-machine having a special winding for the combined generation of a torque and a transverse force. The compensation takes place by a pre-control that acts on the desired force (at the input of the control method) or on the control current, and which is dependent on the flux angle, on the mechanical rotor angle, on the angular velocity of the flux, and on the mechanical angular velocity of the rotor. Additionally, linear and non-linear errors in the control of the transverse force vector such as arise from slot harmonics and winding harmonics and from the material saturation are compensated by a rotation stretching of the control current vector dependent on the flex vector.

Abstract: A rotation position detecting circuit for a sensor-less motor and a motor device include a motor (1) which is rotated and driven by adding a sensor signal having a high frequency to a sine wave drive signal and cosine wave drive signal through adders (5S) and (5C), respectively. Further, a sensor signal is extracted and demodulated from a signal flowing in the motor (1) by a band pass filer (9), and this is defined as a rotation position detection signal. In the sensor signal from the band pass filter (9), its current value is changed corresponding to a change of an impedance resulting from a rotation of a magnet of the motor. As a result, it is possible to detect the rotation position of a rotor magnet by detecting the change of the current value.

Abstract: A second circuit B which is composed of a band-pass filter circuit (5) which takes out a rotating body position signal input from a sensor (1) while scarcely varying a phase within a range including a normal rotation frequency and a reverse rotation frequency of a rotating body, a gain circuit (6) for controlling a gain of an output signal from the bandpass filter circuit (5) and a second notch filter circuit (7) for attenuating components having frequencies lower than the natural frequency of an output signal from a gain circuit (6) is disposed separately from a main circuit A, and an output signal from the second notch filter circuit (7) is positively fed back to the main circuit A through an adding circuit (8).

Abstract: An inertia lowering control apparatus for a two-mass inertia system, the two-mass inertia system having a motor (induction motor), a load of the motor, and a flexible drive shaft having a low rigidity interconnected between the motor and load, is used to suppress an axially torsional vibration occurring on the flexible shaft in the two-mass inertia system. For example, the first-order lag filter having a transfer function as 1/(1+ST.sub.F) is added at an output portion of the Simulator Following Control section which serves as a disturbance suppression circuit together with a shaft torque estimating observer to estimate a shaft applied torque .tau..sub.S. A simulation of the above-described example indicated that even if the observer gain of the shaft torque estimating observer was relatively small, the effect of suppressing the axially torsional vibration was remarkable.

Abstract: A robot comprises a member traveling along a threaded rotary shaft which decelerates when the member approaches a predetermined location on the shaft. Rotation of the rotary shaft is subjected to a resistance imposed by a fluid whose viscosity is increasable by the application of an electrical charge to the fluid. The point at which the rotary shaft begins to decelerate is sensed, and an electrical charge is applied to the fluid to increase its viscosity and attenuate vibration of the member.

Abstract: The invention provides an elastic actuator consisting of a motor and a motor drive transmission connected at an output of the motor. An elastic element is connected in series with the motor drive transmission, and this elastic element is positioned to alone support the full weight of any load connected at an output of the actuator. A single force transducer is positioned at a point between a mount for the motor and an output of the actuator. This force transducer generates a force signal, based on deflection of the elastic element, that indicates force applied by the elastic element to an output of the actuator. An active feedback force control loop is connected between the force transducer and the motor for controlling the motor. This motor control is based on the force signal to deflect the elastic element an amount that produces a desired actuator output force. The produced output force is substantially independent of load motion.

Abstract: The value of a variable reflecting the operating condition of mechanical equipment is continuously detected as operation condition data. A long period average value of the operating condition data detected in long reference period, and a short period average value of data detected in a short analysis period ending in the present time are calculated. Just how much the short period average value differs from the long period average value is adopted as an index of abnormality and using this index, it is possible to ascertain abnormal operating conditions regardless of the absolute value of the variable detected. The above short period average value, long period average value and standard deviation thereof are applied to a first fuzzy membership function for calculating the degree of stability of the mechanical equipment therefrom.

Abstract: A stage driving system capable of positioning an object with a higher speed and a higher precision than prior systems. The system includes a base member, plural movable members provided on the base member, and a controller for controlling the plural movable members so as to substantially suppress the vibration of the base member caused by the displacements of the plural movable members.

Abstract: A magnetic bearing is provided with a simulating circuit for estimating a displacement of a rotor on the basis of a force which is exerted on the rotor. An output of the simulating circuit is compared with an actual displacement signal. A delay circuit and a subtracter are provided to subtract a run-out, which was estimated one period before the rotation of the rotor, from the displacement signal. A displacement signal from which the run-out component was eliminated is set to a new displacement signal. A signal which is obtained by adding an estimated run-out of one period before, namely, an output of the delay circuit to the run-out which was estimated by comparing the output of the simulating circuit with the new displacement signal is newly inputted to the delay circuit.

Abstract: Dimpling of a workpiece by rebounding of a magnetic repulsion punch mechanism, when operated at high punching rates, is avoided by application of a damping pulse at a point at or subsequent to a mid-point of a return stroke of the punch from the workpiece and preferably within the last 10% of the return stroke. This damping pulse is preferably a fraction of the pulse width and of approximately the same amplitude as a driving pulse applying kinetic energy to the punch for causing punching of the workpiece. At high punching rates the kinetic energy of the return portion of a punching stroke is substantially determined by elastic rebounding of the punch from a guide bushing. The removal of kinetic energy during the return portion of the stroke allows the return of the punch to a position close to a rest position during a very short interval with small overshoot under control of mechanical damping.

Abstract: A device for attenuating the periodic vibrations of a mechanical structure adapted to obtain cancellation of periodic vibrations of rotating machines including at least one transducer, detecting original vibrations, delivering a detected signal, a detector of the periodicity of these vibrations delivering a synchronizing signal, and a control circuit and a transducer generating compensation vibrations which are applied to the mechanical structure. The control circuit includes a circuit for synchronous filtering of the detected signal, controlled by the synchronizing signal and delivering a filtered signal whose frequency spectrum contains only the instaneous fundamental frequency of the detected signal. A circuit for regulating the filtered signal delivers an antivibration-control signal applied to a generating transducer in order to minimize the amplitude of the detected signal.