Abstract: For self-switching control of a brushless motor (10) powered by means of a predetermined electrical cycle in order to cause the rotor to advance, the control system comprises an indicator device (100) for indicating the mechanical position of the rotor, the device being associated with a detector device (50) forming an incremental coder device (150) for encoding the mechanical position of the rotor. The system also comprises a motor control assembly made up of processor means (20) for processing the signals coding the mechanical position of the rotor connected to regulator means (30) for powering the plurality of stator windings. The device for indicating the mechanical position of the rotor comprises at least one series (101) of indications of the mechanical position of the rotor corresponding to passing through one electrical cycle of the stator, whereby the incremental coder device (150) delivers the processor means with one synchronization signal for each electrical cycle.

Abstract: A motor controller system for operating a plurality of step motors. The step motors are arranged in a number of motor groups each having no more than “N” step motors. A group multiplexer will deliver feed signals to the correct numbered motor of a motor group. There is a single 1 axis motor control and an output drive for each motor number of a group. The 1 axis motor control supplies the group multiplexer with motor group data so that the group multiplexer will supply the correct motor group and the 1 axis motor control also individually enables the motors of that group which are to be operated and conjointly supplies all the output drives with a desired feed signal.

Abstract: An image reading device reads an image of an original mounted on an original mounting base by using an optical scanning unit which is subjected to acceleration drive along the original mounting base until a velocity according to a reading magnification is obtained and then scanned by uniform velocity drive. A stepping motor moves the optical scanning unit. A reading magnification acceptance portion accepts a reading magnification of an image of the original mounted on the original mounting base.

Abstract: It is an object of the present invention to provide a rotational driving apparatus for a motor vehicle, which moves optical axis of headlights in response to a steering angle of a steering wheel, and which can accurately determine that an output shaft is in good operational order, while accepting errors inevitably taking place. According to the present invention, it is determined that the output shaft of the rotational driving apparatus is operating in a good order, when a first and a second detected voltage at a first and a second detection position are within a predetermined error range and when a deferential voltage between the first and second detected voltages is within a certain deferential voltage span.

Abstract: An electric actuator Includes a first plate and a substantially parallel second plate. A linkage system couples the first plate to the second plate such that moving the linkage system toward an over-center position causes the second plate to move away from the first plate. An electric motor is coupled to the linkage system to move the linkage system toward the over-center position. A force transducer is coupled to the actuator to produce a force signal responsive to a force produced by the actuator. A control system is coupled to the electric motor and the force transducer to provide a control signal to the electric motor to move the linkage system to a position that was determined by the control system in response to the force signal in a previous movement of the linkage system.

Abstract: A circuit for selectively driving n motor coils associated with a plurality of stepping motors, wherein only (n+1) motor coil drivers are needed. A timepiece that utilizes such a circuit is also provided.

Abstract: A control device detects a rotational driving state of a step motor having a coil. First and second switch elements are connected to each other in series, and a node of the first and second switch elements are connected to one side of the coil during use of the control device. Third and fourth switch elements are connected to each other in series, and a node of the third and fourth switch elements are connected to the other side of the coil during use of the control device. A first series circuit has a fifth switch element connected in parallel with the first switch element. A second series circuit has a sixth switch element connected in parallel with the third switch element. A control section controls an on/off operation of the third switch element at a given frequency after a given period has elapsed in a state where the fourth and fifth switch elements are turned on.

Abstract: A stepping motor controller is disclosed that is capable of reducing power consumption of a stepping motor. The stepping motor controller includes a storage unit to store object values of a driving current of the stepping motor, an accumulation unit to accumulate an amount of operation of the stepping motor, and a driving current setting unit to read out an object value corresponding to the amount of operation from the storage unit and set the driving current to the object value. Alternatively, the stepping motor controller includes an accumulation unit that calculates a cumulative amount of operation of the stepping motor, and a driving current setting unit that, when the amount of operation is greater than a predetermined value, determines a critical out-of-step current of the stepping motor by changing in increments the value of the driving current of the stepping motor, and sets the critical out-of-step current with a predetermined margin added as an object driving current of the stepping motor.

Abstract: The present invention provides a control device of a position control motor for preventing step out of the position control motor, wherein the heat generated by the position control motor is small and the energy efficiency is good.

Abstract: A reference signal generation unit generates a reference signal VCA showing a current limit value with a staircase waveform. A PWM control unit compares a measurement signal SENA obtained by a coil current measurement unit with the reference signal VCA at intervals of a PWM timing signal generated by a PWM timing signal generation unit, and switches transistors of a bridge rectification circuit ON and OFF according to the comparison, thereby PWM controlling a supply current to a coil. A discharge instruction signal generation unit issues a discharge instruction signal MMCPA when the reference signal VCA decreases. In response, a PWM control unit forms a current path in the bridge rectification circuit to cause a regenerative current to flow back into a power supply and capacitor.

Abstract: An image scanning device that can be manufactured less costly. When ADF scans an original document (21) loaded in a document hopper (22) of a document feeder unit (12), a stepper motor (M2) is first driven by a motor driver (101) such that it moves a first carriage (50) from a second document scanning start position (P3) to a first document scanning position (P2). The first carriage (50) carries a scanner (14). After that, another stepper motor (M1) is activated by the same motor driver (101) to move the original document (21) over a contact glass (25), and the original document is scanned by the scanner (14). The two stepper motors (M1, 2M2) are selectively driven by the single motor driver (101) so that cost reduction is realized as compared with providing two motor drivers for two stepper motors.

Abstract: A driver circuit is provided for a stepper motor which utilizes a processor that outputs a PWM signal. The driver circuit includes an H-bridge circuit having first and second inputs, and a switching circuit having an input and an output. The first H-bridge input and the switching input connect to the PWM signal output from the processor, and the switching output connects to the second H-bridge input. The switching circuit performs an inversion of a duty cycle of the PWM signal when the PWM signal is present, and a non-inversion of the duty cycle when the PWM signal is not present.

Abstract: A recording apparatus includes a feed roller which feeds a paper sheet, a feed motor which drives the feed roller, and a loss-of-synchronism detecting unit which detects loss of synchronism of the feed motor. When loss of synchronism of the feed motor is detected by the loss-of-synchronism detecting unit, the rotational speed of the feed motor is reduced stepwise. Accordingly, it is not necessary to provide a high operational margin in the motor, and a recording apparatus, in which the motor and power supply costs are reduced, can be provided.

Abstract: A stepping motor driver which drives a stepping motor for position and speed control. The stepping motor driver comprises: a current control means which outputs values corresponding to applied voltages; current sensors which detect phase currents; and a magnetic pole position estimation unit which uses the values corresponding to applied voltages and detected phase current values as outputs of the current sensors to obtain a magnetic pole position estimate. The magnetic pole position estimation unit calculates a magnetic pole position estimate from speed electromotive force estimates or from differences between phase currents at zero speed and detected phase current values.

Abstract: The current in each phase of a multi-phase step motor is monitored and the excess phase current above the set point current, as required on a cycle-by-cycle PWM basis, is reduced thereby bringing each phase current down to the set point. The PWM frequency is automatically adjusted to maintain a minimum number of PWM edges within a portion of the current waveform. A maximum charge/discharge time is specified as a percentage of the PWM period. These provide an accurate independent current control within each phase of a multiphase step motor.

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: A method and apparatus for controlling acceleration and velocity of a stepper motor in which a phase offset is selected depending on motor velocity. The optimal phase offset indicates the position of the winding which generates the maximal driving moment. The increase of the driving force and the extension of the range of steady-state movement is achieved for advanced motor coils commutation with constant frequency using velocity feed back and gradual step-wise phase shift where the phase offset is selected depending on rotor velocity. The invention may be effectively applied to servomotors, stepper motors, motors having certain limitations on movement parameters, such as limitations on acceleration and other types of motors.

Abstract: The integrity of control signals used to control a wafer handling robot is monitored by a monitor connected to various points of the robotic control system. The monitor includes a memory for storing data sets representing correct, reference characteristics of the control signals. The monitor samples control signals at various points in the control system and compares these sampled signals with the stored reference characteristics in order to determine whether a signal disparity exists. If a disparity exists, the monitor generates an error.

Abstract: The sense signal, which is used to indicate that the motor phase current in a stepper motor is at the set point, is marked both before and after each pulse width modulator edge thereby reducing susceptibility to commutation noise from any phase. A mask time is created for a period before and after a PWM edge. The phase current is balanced during this mask time by removing and replacing the phase current.

Abstract: A system and method for controlling a stepper motor system includes selecting a size for at least one step to be taken by the stepper motor system and selecting a direction for the at least one step. Once the size and direction of the at least one step are selected, then at least one trigger signal for the at least one step of the selected size and in the selected direction is generated. The generated at least one trigger signal is transmitted to the stepper motor system to take the at least one step at the selected size in the selected direction. A calibrated display keeps track of the current position of the stepper motor system in response to at least one of the selected size and the selected direction.

Abstract: Stepped rotary motion is imparted to the rotor of a stepping motor by alternately driving at least first and second coils which interact with a plurality of magnetic poles on the rotor. When each of the coils transitions from a driven to a non-driven state, the continued motion of the rotor causes a back electro-motive force to be generated in the coil. The electro-motive forces produced by the coils are rectified, integrated, and then compared with a threshold to determine if a motor stall condition exists.

Abstract: The stepping motor driver comprises an inverter for feeding stepped currents to windings of a stepping motor, a position detector for obtaining a detected angle of a rotor of the stepping motor and a current controller for controlling the inverter. In a d-q rotational coordinate system in which the d-axis is in the direction of the magnetic flux of the rotor and the q-axis is in the direction perpendicular to the d-axis, an excitation angle for a winding is determined from a d-axis component and a q-axis component of a command current to the winding, a lead angle control signal is computed from the excitation angle, and a phase of an applied voltage to the stepping motor is controlled using the lead angle control signal.

Abstract: A first current supplier supplies a first current to a first phase coil of a motor. A second current supplier supplies a second current to a second phase coil of the motor. A current selector selects a value of the first current and a value of the second current, so as to make constant at least one of a magnitude of a synthetic vector obtained by the selected value of the first current and the selected value of the second current at every microstep driving step of the motor, and an angular interval between synthetic vectors corresponding to adjacent microstep driving steps of the motor.

Abstract: A controller for a video surveillance camera enclosure including a method and apparatus for controlling a stepper motor by decoding a command for a specific camera action, setting the state of a state machine, and instructing a position control process and a speed control process based upon the state of the state machine. A drive signal is send from said position control process to a motor current process and a phase control process to generate the current and phase signals to control the stepper motor. The stepper motor drive current is preferably a non-linear current. The speed control signal includes ramp up and ramp down speed control for gradually increasing motor speed and gradually decreasing motor speed, respectively. Another aspect of the invention detects a plurality of pan and/or tilt positions to reset the pan and/or tilt motor step count to a known count associated with a known location without the need to pan and/or tilt past a preselected home position.

Abstract: The stepping motor driver comprises an angle computing element that receives rotor position detection signals from an encoder and calculates a detected angle representing the rotational angle of the rotor, and a lead angle controller that generates a corrected command angle based on the difference between a command angle given from outside and the detected angle. The lead angle controller calculates an angle deviation that is the difference between the command angle and the detected angle, compares the angle deviation with a predetermined value, outputs the command angle as the corrected command angle if the angle deviation is less than the predetermined value, and outputs a value obtained by adding an approximated lead angle to the detected angle as the corrected command angle if the angle deviation is greater than, or equal to, the predetermined value, and the phase of voltage applied to the motor is controlled according to the corrected command angle.

Abstract: Control data is efficiently serially transferred to a drive device for driving a motor without involving the CPU. Data buffers are allocated at specific memory addresses. An address decoder decodes a memory address output to the address bus and applies a write enable signal to the corresponding data buffer to write data to that data buffer by DMA transfer. When data is written to a data buffer, a sequencer circuit compiles control data, based on data in that data buffers, in a shift register, and serially transfers the control data one bit at a time on a serial transfer line synchronized to a clock.

Abstract: A plug and play electric machine interfaces with a plug and play controller. A memory device stores configuration parameters for operating an electric machine that are accessed by the plug and play controller. A plug and play connector connects to the plug and play controller. A sensor monitors a property of the electric machine. A sensor connector communicates with the sensor and the plug and play controller. The configuration parameters are transmitted to the plug and play controller during a power-up sequence of the electric machine. The plug and play electric machine connects to different plug and play controllers. A power connector is associated with the electric machine and communicates with a power driver included in the plug and play controller. The plug and play connector, sensor connector, and power connector form an integrated connector. The plug and play controller updates the configuration parameters based on feedback from the sensor.

Abstract: A reference signal generation unit integrates a staircase signal, to produce reference signal VCTA whose waveform has no abrupt changes in level and which shows a current limit value. A PWM reference signal generation unit generates a PWM reference signal. A supply current measurement unit measures a supply current to a coil. A PWM control unit compares reference signal VCTA with the measurement value of the supply current measurement unit in each period of the PWM reference signal, and sets each transistor in a bridge rectification circuit in a conducting state or a nonconducting state according to the comparison result. In this way, the supply current to the coil is controlled to approach the current limit value shown by reference signal VCTA.

Abstract: Methods and devices are disclosed for identifying objects over a surface and for tracking the position of said objects in relation to the sensing surface. The methods include the steps of providing an array of electrodes or coils that generating electromagnetic radiation having a individual characteristic frequencies of oscillation. Objects in proximity to the sensing surface(s) couple electromagnetically to the array of electrodes or coils, which then alters the characteristic frequency of one or more elements in the array. By monitoring the individual frequency shifts among the array elements, one or more objects in proximity to the surface can be sensed and identified. Quantitative identification and enhanced detection of the objects is achieved through the use of electromagnetic markers affixed or embedded in the objects in specified geometric patterns.

Abstract: A stepping motor control circuit sets the setting values of each defining a driving pulse period corresponding to a number of velocity steps at the time of accelerating or decelerating a stepping motor in a register, and performs calculation so as to divide each difference between driving pulse periods in between respective setting values into a predetermined number of pieces to change the driving pulse period. By doing so, this smoothly controls the acceleration and deceleration of the stepping motor without enlarging circuit scale and stepping out even if there is no excessive torque margin.

Abstract: A motion control system and method are disclosed which provide improved pulse placement for smoother operation of a motion device such as a stepper motor. A placement of pulses may be determined for each of a plurality of time intervals such that the pulses are placed evenly across the plurality of time intervals, wherein the quantity of pulses in each of the time intervals is variable. The pulses may be generated and sent to the motion device to move the object to the desired position. A delay may be used to place each pulse at an arbitrary location within one of the time intervals. Where the desired step rate is fractional, time may be “borrowed” for one loop iteration from other loop iterations. In one embodiment, the step rate may be changed from one loop period to the next.

Abstract: In controlling a motor in a device which drives a mechanism using the motor as a power source, pre-driving of giving a predetermined driving parameter to the motor and driving the mechanism is executed. During the pre-driving, movement of the mechanism is monitored, and a command value to the motor, which is necessary for starting the mechanism, is obtained. Driving of the motor is controlled using feedback using the command value as the initial value of the driving parameter. High-speed accurate position control can be achieved independently of the individual difference in an object to be controlled and the frictional force of the mechanical portion or the difference in use environment.

Abstract: Methods, devices and circuits for detecting malfunctions in stepper motors. A signal from a driver circuit to a stepper motor that is proportional to the current in the windings of the stepper motor is detected. This signal is then amplified and integrated for ease of comparison. The resulting signal is then compared to a specific entry in a table of values with each entry in the table corresponding to an operating profile of the stepper motor. If the resulting signal does not correspond to the operating profile for which the motor a configured, the stepper motor is jammed. A suitable alarm and a corresponding sequence of actions may then be triggered.

Abstract: A vehicle drive assembly includes an electric motor directly coupled to a rotatable member for driving a wheel, for example, without gear reduction assemblies between the motor output and the driven wheels. A multi-phase, high pulse current stepper motor is used as the motor in one example. A driven wheel is supported by a wheel mounting member in a conventional fashion. A rotatable member associated with the wheel mounting member is directly coupled to an output of the stepper motor. The stepper motor can selectively operate in several modes. A first mode provides driving torque to the vehicle wheels, a second mode provides a braking force and an optional third mode allows the stepper motor to serve as a parking brake.

Abstract: It is an object of the present invention to provide a rotational driving apparatus for a motor vehicle, which moves optical axis of headlights in response to a steering angle of a steering wheel, and which can accurately determine that an output shaft is in good operational order, while accepting errors inevitably taking place. According to the present invention, it is determined that the output shaft of the rotational driving apparatus is operating in a good order, when a first and a second detected voltage at a first and a second detection position are within a predetermined error range and when a deferential voltage between the first and second detected voltages is within a certain deferential voltage span.

Abstract: There is provided a print control unit capable of transferring and stopping an object to be controlled at a target position when unexpected load is applied to the object. A print control unit includes: a selection control part, operating at a predetermined timing, to select and set the control parameters in accordance with the target speed, to judge as to whether the object is located within a target range, based on the output of the position detecting part, if located, the selection control part selecting and operating the third control part, while if the object is not located within the target range, the selection control part selecting and operating the first or the second control part based on the physical value corresponding to the speed.

Abstract: A stepper motor control circuit reduces ripple current by applying both fast and slow current decays to a motor phase when current is being reduced in the motor phase while following a falling current waveform. The control circuit uses an initial fast decay to reduce a winding current and then switches to a slow decay until a winding current is sampled again. The control circuitry samples a winding current and compares the sampled current to a reference current to determine if current is to be applied or reduced using fast and/or slow decay methods. Different phase current sample circuits allow either constant current sensing or selective current sensing.

Abstract: The invention concerns a control system for a d.c. motor (10), powered by an actuating system (14) comprising: a position detector (30, 32) co-operating with the motor's rotor; a power supply circuit (34) to apply to the terminals of the motor coils a supply voltage to generate the electric current, and a control circuit (36). This system is designed to actuate the motor to move a moving part (24), with a view to reaching a target position Pc defined by a number of steps dc to be executed. During a so-called positioning phase, the control circuit (36), after observing that target position Pc has been reached, interrupts the current powering the coils and applies to them a braking pulse (If) of reverse polarity, then short-circuits them until stoppage observed by the detector (30, 32).

Abstract: To reduce power consumption without braking a step motor. In a given period after transistors are turned on and a motor is rotationally driven, the transistors are turned on, and the other transistors are turned off, and after the given period has elapsed, the on/off operation of the transistor is controlled at a given frequency in a state where the transistors are maintained in an on state, to thereby detect whether or not the motor rotates. Also, In a given period after the transistors are turned on and the motor is rotationally driven, the transistors are turned on and the other transistors are turned off, and after the above given period has elapsed, the on/off operation of the transistor is controlled at a given frequency in a state where the transistors are maintained in the on state, to thereby detect whether or not the motor rotates.

Abstract: A motor controller comprising, a detector configured to perform a difference processing for information relating to a counter electromotive force and an induced electromotive force generated by a stepping motor, and to generate a driving control signal based on a result of the difference processing, and a driver configured to drive the stepping motor based on the driving control signal.

Abstract: A controlled stepping motor is electrically connected to a controller and a loading device. A method of controlling the stepper motor includes utilizing the controller to output a control signal to the stepping motor according to a target displacement and a first index parameter, utilizing the stepping motor to move the loading device according to the control signal, utilizing the controller to calculate a difference between the target displacement and an actual displacement of the loading device, and utilizing the controller to generate a second index parameter for updating the first index parameter according to the first index parameter, the difference, and the actual displacement.

Abstract: A vehicle drive assembly includes an electric motor directly coupled to a rotatable member for driving a wheel, for example, without gear reduction assemblies between the motor output and the driven wheels. A multi-phase, high pulse current stepper motor is used as the motor in one example. A driven wheel is supported by a wheel mounting member in a conventional fashion. A rotatable member associated with the wheel mounting member is directly coupled to an output of the stepper motor. The stepper motor can selectively operate in several modes. A first mode provides driving torque to the vehicle wheels, a second mode provides a braking force and an optional third mode allows the stepper motor to serve as a parking brake.

Abstract: When excited states of excitation coils are controlled at a both excitation step of magnetizing both of two excitation coils, an initializing driving means 41a inputs excitation pulses in which a duty ratio thereof at an interval of time controlled by the both excitation step is less than 1 to the excitation coils. Contact detecting means 42 detects contact based on voltages generated at the excitation coils when the excitation pulses are not inputted.

Abstract: To more surely detect the presence/absence of the rotation of a step motor with a simple structure. In a first detection period immediately after stopping driving of the motor, transistors turn on, the on/off operation of a transistor is controlled at a given frequency, and a detection signal generated in a resistor is taken out from a terminal. Because a current flows in an opposite direction of an equivalent diode of the transistor, the detection signal in the case where the motor does not rotate is suppressed to a low voltage that is equal to or lower than a threshold value. In a second detection period immediately after lapse of the first detection period, the transistors turn on, the on/off operation of the transistor is controlled at a given frequency, and a detection signal generated in a resistor is taken out from the terminal.

Abstract: A stepping motor driver which drives a stepping motor for position and speed control. The stepping motor driver comprises: a current control means which outputs values corresponding to applied voltages; current sensors which detect phase currents; and a magnetic pole position estimation unit which uses the values corresponding to applied voltages and detected phase current values as outputs of the current sensors to obtain a magnetic pole position estimate. The magnetic pole position estimation unit calculates a magnetic pole position estimate from speed electromotive force estimates or from differences between phase currents at zero speed and detected phase current values.

Abstract: A single-body structure is presented for use as a tool tip for making modifications and/or collecting measurements on a target object. The single-body structure comprises a first end portion, a second end portion opposite the first portion, and a mid portion between the first and second end portions, wherein a central axis can be defined extending from the first end portion to the second end portion, and wherein the single-body structure has a maximum linear dimension of approximately 50 microns or less. The single-body structure may be comprised of diamond. One of the first and second end portions may have a larger cross sectional area, in a plane perpendicular to the central axis, than does the other of the first and second end portions. One of the first and second end portions may have a larger cross sectional diameter, in at least one direction perpendicular to the central axis, than does the other of the first and second end portions.

Abstract: A shutter mechanism includes a drum (2), a stepping motor (5), a driver (20), a microcomputer (10), a memory (16), and a load magnitude detection circuit (30) that detects the magnitude of the load on the stepping motor (5) when an object such as a shutter (3) is either wound or unwound from the drum (2). The microcomputer (10) can set the upper and lower limit stopping positions of the shutter (3) by resetting the number of command pulses stored in the memory (16) when the load magnitude detection circuit (30) detects an increase in the load at the stepping motor (5), and storing the number of command pulses output to that point from the memory (16) when the load magnitude detection circuit (30) next detects an increase in the load at the stepping motor (5) after the outputting of the command pulses is next restarted.

Abstract: A stepping motor control apparatus that is able to electrically detect the load of the stepping motor and effectively prevent step-outs by means of an inexpensive configuration. The stepping motor control apparatus is equipped with a microcomputer (10) that outputs a command pulse, a chopper-type constant current driver (20) that outputs a drive current that corresponds to the input command pulse to the stepping motor (5) and outputs a chopper signal to keep the output drive current fixed, and a load detection circuit (30) that detects the chopper signal to detect the load of the stepping motor (5). The load detection circuit (30) is equipped with a waveform shaping circuit (50) that makes the chopper signal waveform continuous to convert it to a pulse or voltage, and it detects the load of the stepping motor by means of the width of the pulse or the voltage value.

Abstract: An abnormality detector for motor drive system easily detects, using a CPU, abnormality such as short circuit or disconnection in magnetic field coils of a motor, wiring, an open/close element, etc., which are controlled by a microprocessor (CPU). The open/close elements conducting an open/close operation sequentially in response to pulse outputs P1, P2 generated by the CPU, drive the magnetic field coils. Surge voltages generated upon interrupting the mentioned open/close elements are OR connected through a diode, and input to a temporary storage circuit. Then the CPU reads out, stores and resets the surge voltages using pulse edges of the pulse output P1 or P2. When any generation of the surge voltage is not stored in the temporary storage circuit, the CPU operates an abnormality alarm display.

Abstract: A method and system for calibrating a motor-driven instrument pointer (8) against a stop (5) without using feedback includes, in a first power state, driving the pointer (8) at full torque against the stop (5), then driving the pointer (8) against the stop at a reduced torque for a predetermined radial distance so at the pointer (8) is caused to be held against the stop (5). A third driving step, at reduced torque for a further predetermined radial distance, may be used in a second power state to move the pointer (8) against the stop (5).