Abstract: A system for controlling a flow rate through an HVAC component is provided. The system includes a controller communicably coupled with a potentiometer and an actuator configured to drive the HVAC component between multiple positions to affect the flow rate. The controller configured to determine an actuator position setpoint based on a flow rate setpoint, drive the actuator to the actuator position setpoint using a calculated travel period, and set a current actuator position based on a voltage signal received from the potentiometer upon stopping the actuator at an expiration of the calculated travel period.

Abstract: A low cost and efficient method and apparatus for calibrating high performance internal permanent magnet motors that involves starting from an initial estimation of the rotor position and improving the estimation incrementally by successively commanding various current vectors and making adjustments to the estimated initial position according to the rotor's physical reaction to such current vectors.

Abstract: Methods and systems are provided for a winch including a motor and a contactor assembly positioned within a same housing. In one example, the contactor assembly is positioned at an end of an armature of the motor and may include a controller configured to control winch component operation. The contactor assembly is electrically coupled to the armature via a plurality of electrically conductive brushes.

Abstract: A locking system for a cabinet may include a plurality of hubs to pass signals from activation devices and for power distribution to locks controlling access to drawers and/or openings of the cabinet. The hubs may also pass signals between pairs of locks, for example for drawer slides used for drawers of the cabinets. In some embodiments the hubs passively pass the signals, and in some embodiments each of the hubs are identical.

Abstract: Weighing system (FIG. 3, FIG. 6) to weigh items, parcels and the like while they are moving, for example, on a conveyor. A servo amplifier (14) and servo controller (20) are arranged to drive a servo motor in a feedback (15) configuration, and acquire torque sensing signals (17) responsive to commanded acceleration of the conveyor while the item(s) are on board. Preferably, constant acceleration of the item(s) is realized during one or more measurement intervals, and mass is derived by a processor (30) based on the measurement data (FIG. 5). Other embodiments are described for weighing granular and slurry materials (FIG. 7) and for weighing multiple, potentially overlapping, parcels in motion (FIG. 8).

Abstract: A starter which includes a shift piece that is relatively rotatably fitted to a groove (6) of a clutch and is also relatively rotatably coupled with a straddle portion of a shift lever (9), for joining the clutch and the shift lever together, so that a pinion gear is engaged with or released from a ring gear by a reciprocal movement of the clutch that is in conjunction with pivotal seesaw motion of the shift lever (9), wherein the shift piece is configured separately by a ring-like shift piece (7) mounting to the groove (6) of the clutch and a shift piece B (8) mounting to the shift lever, which are mounted in a form coupled together.

Abstract: A control system is provided for starting electrically powered implements on a vehicle such as a grass mowing machine with electrically powered cutting reels. The electric motors are started at intervals, rather than simultaneously. The intervals between starting each electric motor may be based on pre-defined criteria such as a fixed time constant, voltage, current or speed input from a motor controller for each implement.

Abstract: The invention relates to a method for controlling a motorized flap, wherein the flap arrangement comprises a flap which may be a pivotable flap, a drive arrangement associated with the flap and a control arrangement associated with the drive arrangement, wherein the deflection of the flap is limited in at least one first direction of movement, by a mechanical end stop on the motor vehicle side, wherein the motorized flap movement in the first direction of movement is limited by means of the control arrangement by an end stop provided by control technology, in order to prevent the flap from running in a motorized manner in the first direction of movement into the mechanical end stop.

Abstract: The present invention relates to a self-propelled working machine, especially in the form of a surface milling machine, such as asphalt-milling machine or snow-milling machine comprising a main operating unit and/or a drive unit, which is operable in a steady-state or near steady-state operating status and is drivable by a drive device comprising at least an electrical motor, the electrical motor being associated with a start-up including a frequency converter for the limitation of starting current. The invention also relates to a process for operating such a self-propelled working machine. According to the invention an operating circuit for steady-state operation is provided, comprising a jumper for bridging the frequency converter following starting or reaching steady-state operational status. Optionally, the jumper is switchable to activate or inactivate the frequency converter of the start-up circuit, respectively.

Abstract: A method for connecting a second motor to a variable speed drive in parallel with at least one existing motor under load and controlled by the variable speed drive is provided. The method disconnects the existing motor from the variable speed drive and a state estimator calculates transient state of the existing motor including at least the speed of the existing motor based on a previously established load model. The method then connects the second motor to the variable speed drive and the second motor is operated using a suitable directive until the actual state of the second motor attains the calculated transient state of the existing motor at a given time. Upon attaining the calculated transient state, the existing motor is reconnected to the variable speed drive such that no current spike is generated in the aforementioned process.

Abstract: A fan control system includes a fan and a fan control circuit. The fan control circuit includes a connector, a control unit, a switch unit, and a delay unit. The control unit is connected to the connector to receive a rotation speed control signal, and connected to the fan. The switch unit is connected to the connector to receive a voltage signal, and connected to the control unit. The delay unit is connected to the connector to receive the rotation speed control signal, and connected to the switch unit. When the delay unit receives the rotation speed control signal, the delay unit outputs a control signal to turn on the switch unit after a time delay, the voltage is transmitted to the control unit through the switch unit, the fan operates, the control unit controls rotation speed of the fan according to the rotation speed control signal.

Abstract: A fan control system includes a fan and a fan control circuit. The fan control circuit includes a connector, a control unit, a switch unit, and a delay unit. The control unit is connected to the connector to receive a rotation speed control signal, and connected to the fan. The switch unit is connected to the connector to receive a voltage signal, and connected to the control unit. The delay unit is connected to the connector to receive the rotation speed control signal, and connected to the switch unit. When the delay unit receives the rotation speed control signal, the delay unit outputs a control signal to turn on the switch unit after a time delay, the voltage is transmitted to the control unit through the switch unit, the fan operates, the control unit controls rotation speed of the fan according to the rotation speed control signal.

Abstract: A method for connecting a second motor to a variable speed drive in parallel with at least one existing motor under load and controlled by the variable speed drive is provided. The method disconnects the existing motor from the variable speed drive and a state estimator calculates transient state of the existing motor including at least the speed of the existing motor based on a previously established load model. The method then connects the second motor to the variable speed drive and the second motor is operated using a suitable directive until the actual state of the second motor attains the calculated transient state of the existing motor at a given time. Upon attaining the calculated transient state, the existing motor is reconnected to the variable speed drive such that no current spike is generated in the aforementioned process.

Abstract: Method and arrangement for connecting an AC electric motor (M1, M2, . . . MN) to an AC electricity network (L) in a system which comprises a frequency converter (FC), with which the motor is started, and contactors (S11, S12, S21, S22, SN1, SN2), in which method the supply source is changed by means of the contactors from the frequency converter to a direct network supply, in which method the frequency converter is stopped before changing the supply source, and in which method in connection with changing the supply source the control of the contactors is started before stopping the frequency converter.

Abstract: Permanent magnet alternating current (PMAC) motor systems and methods for starting or restarting PMAC motor system sensorless control algorithms are provided. One system includes a PMAC motor including a rotor, an inverter, and a controller. The controller includes control logic, start/restart logic, drive logic, current detect logic, and estimation logic configured to estimate a position of the rotor, a speed of the PMAC motor, or both based on current detected in each phase of the inverter. A start/restart method includes determining to start/restart the sensorless control algorithm and modifying the inverter voltage in response to the determined start/restart. The method also includes detecting current in each inverter phase after the inverter voltage is modified and estimating a rotor position, a PMAC motor speed, or both based on the current detected in each inverter phase after the inverter voltage is modified. Another controller includes means for performing the above start/restart method.

Abstract: A method of selectively utilizing a set of linear actuator motors for an application includes providing a plurality of linear actuator motors numbered from 1 to N including a box shaped housing with respective lengths between a first end-plate and a second end-plate and respective hollow shafts. Each hollow shaft includes an extended portion out of either the first end-plate or the second end-plate and configured to receive a nut including a tube part integrally connected with a flat-end part. The nut is configured to be able to mate in a common manner to any of the plurality of linear actuator motors. The method further includes testing any of the plurality of linear actuator motors including the nut for the application, wherein the nut is detached from one linear actuator motor to reattach with another linear actuator motor.

Abstract: A control circuit for a washing machine that avoids contact bounce short circuit failures is provided. A washing machine that utilizes an induction motor including a starting winding used to start rotation of the motor at the beginning of a cycle. Such washing machines require that the motor be operated in both directions during different cycles. To enable such operation, a mechanical timer uses a pair of single pole, double throw switches in a switching assembly to reverse the L1 and neutral connections to the starter winding. To avoid the contact shorting problem, the control wiring runs either the L1 or neutral side of the voltage source, or both, through the centrifugal switch to open the input contact(s) once the motor has reached its operating speed. Then, if the switching assembly has L1 and N contacts touching at the same time, it will not result in a dead short.

Abstract: A method to start at least two AC motors that are supplied from a common AC bus, which in turn is supplied from a power converter. At least one of the AC motors is an electrically excited synchronous motor including an excitation circuit. The synchronous motor is started first. During starting of remaining of the at least two AC motors a reactive power supplied by the power converter is determined and an increase of a field current or of a field voltage of the synchronous motor in linear dependence on the reactive power supplied by the power converter is determined. The increased field current or field voltage is applied to the excitation circuit of the synchronous motor.

Abstract: Method and arrangement for connecting an AC electric motor (M1, M2, . . . MN) to an AC electricity network (L) in a system which comprises a frequency converter (FC), with which the motor is started, and contactors (S11, S12, S21, S22, SN1, SN2), in which method the supply source is changed by means of the contactors from the frequency converter to a direct network supply, in which method the frequency converter is stopped before changing the supply source, and in which method in connection with changing the supply source the control of the contactors is started before stopping the frequency converter.

Abstract: The lighting fixture includes a housing having an interior cavity and a transparent cover. A color-changing electric light assembly is provided in the interior cavity. The light assembly emits a plurality of different colors of light through the transparent cover and cycles through the plurality of different colors of light to sequentially emit each of the plurality of different colors of light. A synchronization circuit responds to a timed interruption in the power for synchronizing the color-changing electric light assembly with a color-changing electric light assembly of another underwater lighting fixture connected to the same power.

Abstract: An electric motor selectively connectable to receive one of a plurality of supply voltages, the plurality of supply voltages comprising a low supply voltage and a high supply voltage. The motor can comprise a stator having a first winding and a second winding, a shaft rotatable about a motor axis, and a rotor supported by the shaft for rotation with the shaft relative to the stator. The motor can also comprise a voltage selection device, a first motor protector, and a second motor protector. The voltage selection device can include a first setting and a second setting and can be configured to connect the first winding in parallel with the second winding when set to the first setting and to connect the first winding in series with the second winding when set to the second setting. The first motor protector can be configured to limit current through the first winding and the second winding when an overload condition exists.

Abstract: An underwater lighting fixture adapted for installation in a lamp receiving recess in the wall of a swimming pool. The fixture includes a lamp housing having a pair of reflector-mounted incandescent lamps mounted therein. A plate having a pair of a apertures is mounted in the housing with the apertures mounted in alignment with the lamps. A pair of secondary reflectors are mounted to face the plate apertures and are provided with light-transmitting portals. A color wheel having dichroic filter segments is mounted so that identically colored pairs of segments pass the portals when the color wheel is driven by a motor. The motor is controlled by a circuit by disconnecting power to an input of the circuit, reconnecting power to the input to control the motor to move at a first speed. The control circuit stops the motor when the driven element reaches an index position.

Abstract: To resolve a problem of the repairing of an electronic system, a machine will undergo a learning stage during the replacement of a part of the machine. This learning stage can be monitored manually or automatically on a limited range of variation. During this learning stage, readings are taken of the resultant modifications on a structure of the membership functions and of interference rules, memorized in a fuzzy logic program that controls the machine. These membership functions and/or theses rules are then modified as a function of this results. It is shown that it is possible, in this way, to repair a machine without replacing a defective part by a strictly identical part and without having to bring the machine back to the laboratory.

Abstract: A rotational angle detecting apparatus [reduces the influences of a rotational angle detection error included in a linear slope portion of a detection signal when detecting a fine rotational angle, thereby achieving highly accurate detection of rotational angles. The rotational angle detecting apparatus includes] having a rotation detector that outputs, as a rotor coupled to a rotating member rotates, first and second detection signals, which [has a] have predetermined amplitudes, the same cycle, and a phase difference of a quarter wavelength, a memory for storing the first and second detection signals, and a control unit.

Abstract: In an opposed wiping type wiper apparatus, left and right wiper blades which perform wiping operations with a predetermined preceding-following relationship maintained are layered vertically at their lower returning positions. A wiper drive control unit controls preceding-following relationships between the left and right wiper blades to prevent locking and stopping of the wiper blades when the relationship has changed by replacing left and right control forms for the blades. When the timer of the wiper blade which is to be in the follower side during normal operation is not reset but overflows among timers which are respectively reset pulse signals generated in accordance with rotations of motors, the output of the motor which drives the wiper blade which is to be in the follower side during normal operations is increased.

Abstract: Only a small useful quantity of washing water as close as possible to the spray nozzles of the windshield wiper system is heated. As a result of corresponding miniaturization, the heating time can be reduced to 5 to 10 seconds. A sufficient cleaning effect can be achieved in most cases by hot water after the windshield spray system is actuated two or three times. Additional cleaning can be carried out either by rinsing with colder or cold water or by repeating after 10 to 20 seconds. The water is heated via an instant heating element which, with a content of, for example, 10 to 50 cm.sup.3, can be installed even in a secondary chamber. Some of the heat energy is therefore stored in a larger thermal reserve tank of, for example, 1 dl.

Abstract: The common contact 5a of a power source circuit side relay 2a is connected to the common contact 15a of a motor circuit side relay 12a. The common contact 5b of a power source circuit side relay 2b is connected to the common contact 15b of a motor circuit side relay 12b. And, the switching contacts 6a and 6b, and 16a and 16b of the power source circuit sides relays 2a and 2b and the motor circuit side relays 12a and 12b are tripped in response to relay switching signals provided by an ECU. The power source circuit side relays 2a and 2b are selectively switched, so that the directions of flow of currents in the motor circuits 21 through 24 are changed.

Abstract: A method and apparatus for operating a positioning device for an adjustable device. The positioning device is mechanically actuated by a bearing connected to a pivotable armature that interacts magnetically with an electromagnet. The electromagnet is energized by current pulses generated by a computer program. The current pulses cause the air gap between the pivotable armature and the electromagnet to vary between open positions where the electromagnet is not magnetized, and a closed position where the electromagnet is magnetized. Several bearings and associated electromagnets may be arranged to operate the positioning device in one or more directions and at different torques and operating speeds for different directions of operation and different positions of adjustment.

Abstract: A highly flexible electronic control system which is readily reconfigurable or reprogrammable to suit more than one machine, such as more than one laundry appliance. Control parameters are input to the controller over a communications link, which may be an optical communications link. The controller is automatically adaptable to particular ones of a plurality of different machines, for example laundry appliances in the form of a two-speed washer, a one-speed washer, an electric dryer and a gas dryer. The controller determines the particular appliance by applying signals to particular terminals of a connector connected to a machine to be interrogated. Other terminals are monitored to logically recognize the particular appliance. Thereafter, the control system implements functions appropriate to the particular appliance.

Abstract: A method and firmware motor calibration system for measuring average system voltage of operating electric motors and time of movement between physical stops of mechanical structures coupled to the output shafts of the electric motors. The system calibrates motors arranged to operate as hybrid closed and open loop motor control systems. Data concerning position of the shafts is determined for the closed loop motor control systems.

Abstract: A universal electrical control selectively drives either plural motorized window operators for opening or closing one or more windows, or a motorized window operator and plural motorized locks for opening, closing and locking a window. The electrical control comprises an interface circuit for connection to plural output devices comprising either motorized window operators or motorized window locks. An input switch commands window movement to an open or close position. A control circuit is connected to the interface circuit and the input switch and includes an initialization mode for determining if each output device is a motorized window operator or a motorized lock, and output drive mode operable in response to a command from the input switch for driving the output devices through the interface circuit in a lock sequence or a window sequence dependent upon the initialization mode respectively determining if a motorized window lock is connected or is not connected to the interface circuit.

Abstract: An ornamental closure which opens to a scene and includes animated scenes moved into view from within the closure. Mechanisms and electrical circuitry provide the power to operate the closure and to provide music during operation. A plurality of such closures are programmed to operate sequentially and may include hangers to secure them to the branches of a Christmas tree.

Abstract: An electric control for gas furnaces which controls a two speed main blower fan and an induction draft fan based on inputs from a room thermostat, a high limit and an ignition control including a gas valve. The control has a circuit board having a power supply for providing 24 volts DC current source to drive DC relays and a 5 volt DC power source to power a microprocessor. 24 volt AC input signals are coupled to the input ports of the microprocessor through current limiting resistors and to AC ground through pull down resistors. AC ground is also connected to the IRQ port of the microprocessor. The output ports of the microprocessor are connected to a relay driver which in turn is connected to the relays. Several breakaway tabs in the board provide optional features such as eliminating a normally provided draft delay timing function. Test pads are provided on the board so that the board can be tested during manufacture.

Abstract: A wiper apparatus comprises a wiper switch, a washer motor, a washer switch for actuating the washer motor by its on-operation, a wiper motor actuated independently by on-operation of the wiper switch and interlockingly with the washer motor by the on-operation of the washer switch, and a controller for maintaining the wiper motor to rotate until the load applied on the wiper motor reaches predetermined value. According to this invention, the wiper blade never stops before the cleaning liquid is removed from the wiping surface by detecting frictional resistance between the wiper blade and the wiping surface as the motor load.

Abstract: A disk chipper for the production of wood chips, consisting of a rotatable chipping disk supported on an axle driven by at least one drive machine. The disk chipper of the invention is so implemented that at least three motors are drivably coupled to the axle of the chipping disk by means of a gear assembly, preferably a spur gear assembly.

Abstract: An electric motor drive system having a first electric motor, a first drive shaft to which the first electric motor is coupled, a second electric motor having a higher power rating than the first, a second drive shaft to which the second electric motor is coupled, an epicyclic gear system comprising a sun gear to which the first drive shaft is coupled, a ring gear to which the second drive shaft is coupled, and planetary gears meshing with both the sun gear and the ring gear, an output drive coupled to the planetary gears, and, a one-way rotation restraining means coupled to the second shaft to permit rotation of the second shaft in one direction and to prevent rotation of the second shaft in the other direction for restraining motion of the second shaft during start up of the first motor, and a one-way rotation restraining means coupled to the first drive shaft for restraining rotation of the first shaft during start up of the second motor, and clutch means operable to interconnect said first and second moto

Abstract: A flat frequency, constant voltage power source device is provided for parallel operation of a plurality of electric generators. The generators include exciting windings of induction motors integral with the generators for connecting and disconnecting outputs of the generators. A starting sequence of the electric generators is based on a start signal provided externally and start preparation completion signals indicating completion of start preparation routines. The induction motors of the generators are thereby varied in frequency so that the generators can be synchronized in phase for their effective parallel operation.

Abstract: A control for a window operator is operable to control incremental movement of a window. The control includes means for developing a command to selectively move the window in a direction to an open or closed position, and means for determining when a plurality of motor drives have moved the window a preselected incremental distance. Means are coupled to the developing means and the determining means for energizing each of the motor drives if a command is developed, until the motor drives have moved the window the preselected incremental distance and thereafter deenergizing the motor drives until another command is received to move the window a subsequent incremental distance in the selected direction.

Abstract: A pair of wiper blades on a vehicle window are oscillated in opposing movement between an overlapping inner wipe arrangement, in which one of the blades overlaps the other, and separated outer wiper positions. In dynamic symmetrical overlap (DSOL) operation, the first blade during each cycle to reach its outer wipe position is brought back first to be overlapped by the other for the start of the next cycle. This will normally produce alternating symmetrical overlap (ASOL) operation with its advantages of lower maximum blade acceleration and stress, since the overlapping blade precedes the other on the way out. However, if the leading blade is occasionally slowed, the other blade will not be forced to wait in its outer wipe position; and the cycle time will be minimized.

Abstract: A pair of wiper blades on a vehicle window are oscillated in opposing movement from an overlapping inner wipe arrangement, with upper and lower overlapped blades, outward to separated outer wipe positions and inward to the overlapping inner wipe arrangement with the positions of the blades reversed. Since the upper blade on the way out becomes the lower blade on the way back, it does not need to pause in its outer wipe position and it thus does not need to be subjected to a large acceleration in maintaining fast wipe cycles on large vehicle windshields. This reduces stress on the arm and blade and blade end whip.

Abstract: A method of starting series-coupled vacuum pumps comprising a primary pump (A) and at least one secondary pump (B) connected between the primary pump and an enclosure (E) in which a vacuum is to be established, the method consisting in starting the primary pump initially and subsequently starting the secondary pump when the suction pressure of the primary pump as reduced by rotation of the primary pump reaches an acceptable value, the method being characterized in that the pressure existing in the secondary pump is determined by using a physical magnitude related to the primary pump and following a law similar to the pressure law.

Abstract: A motor control system for controlling operation of a plurality of motors. The motor control system is composed of a microcomputer for performing sequential control of the motors. A plurality of integrated circuits are provided to drive the motors, respectively, in response to signal output from the microcomputer. Each integrated circuit has two input terminals connected respectively to two output ports of the microcomputer and two output terminals connected respectively to one terminals of the motors. Additionally, a change-over circuit is provided to change over the rotational direction of the motors in response to signals from the microcomputer.

Abstract: A control for an electrically powered, motor vehicle windshield wiper system with independent drive motors for the wiper blades which produces an opposing wiper pattern with overlapping park and which is simple and inexpensive to manufacture by providing a unique switching system which coordinates the blades to prevent interference therebetween and converts simply and effectively, when the system is turned off, to a blade parking control which allows continuation of normal blade movement into a predetermined park position. The control provides switch control for the motor of each wiper blade in response to certain predetermined positions of the other blade, including, in particular, a position adjacent but outside the wipe pattern of the other blade wherein the controlled blade may be stopped if necessary to avoid interference.

Abstract: An electronic motor includes a shaft mounted for rotation about a rotational axis. A plurality of radial lever arms are mounted with respect to the shaft. Each lever arm has an inner end connected to the shaft by a one-way clutch. The clutches allow the shaft to rotate in only a first circumferential direction with respect to the lever arms. An electrically conductive element is attached to an outer end of each lever arm. A drive coil is positioned adjacent to each electrically conductive element. A drive circuit periodically and sequentially energizes each drive coil with current pulses. Each drive coil is oriented to produce a first pulsed magnetic field in a direction generally tangential to the circumferential direction when energized. The first magnetic field induces circulating currents within the electrically conductive element. The circulating currents in turn produce a second magnetic field about the electrically conductive element.

Abstract: A control system for a booster type belt conveyor having one or more booster belts spaced at intervals along a conveyor belt with the upper, driving run of each booster belt frictionally engaging the underside of the conveyor belt carrying run. Each belt has a driving pulley connected to a driving unit including one or more electric motors, engageable and disengageable fluid couplings, and a gear box. The conveyor is for heavy duty service, in long lengths of several miles. There is an electrical control assembly for each drum or pulley driving unit. These automatically start the motors in sequence while the couplings are disengaged, each being started in response to a signal from a previously started motor that it has reached running speed. An electrical loop interconnects all the control assemblies and contains relays which, when the loop is energized to actuate the relays, cause the fluid couplings to engage.

Abstract: A pulse motor driving apparatus is comprised of a timer circuit generating a slue-up pulse and a normal operation pulse, latch circuits latching a phase designating signal in synchronization with the slue-up pulse and normal operation pulse of the timer circuit, and driving circuits driving pulse motors in response to the latched, phase designating signal of the latch circuits. The timer circuit is comprised of first and second counters for generating the slue-up pulse and normal operation pulse. In the slue-up operation mode, two of the pulse motors are driven in synchronization with the output pulses of the first and second counters. Upon completion of the slue-up operation, the two pulse motors are driven in a normal operation mode, in synchronization with the output pulse of the first counter.

Abstract: An inertial measuring unit gyroscope wheel dynamic braking and sequence inhibiting circuit is disclosed. The circuit comprises a first counter for counting a specified time interval and digital logic circuitry for applying an in-phase signal to the phases of a multiphase electric induction motor driving a gyroscope wheel during the time interval, for example, a vertical gyroscope motor wheel. By placing in-phase signals on the inputs of a multiphase electric induction motor, the motor is brought completely to rest in a short time by dynamic braking. In a preferred embodiment, a second counter counts a second specified time interval after the first time interval has terminated, during which second time interval a second electric induction motor is dynamically braked, for example, an azimuth gyroscope wheel motor. During the time period when the motors are braking, a signal is fed back to an automatic sequencing circuit to inhibit further sequencing of the inertial measuring unit.

Abstract: An apparatus for use in an automatic door system. Means are provided which compares the current position of the running door with a deceleration point to generate a low speed command upon their coincidence. A speed control responds to decelerate the door to a selected low speed. A measuring device measures a variable run-length of the door which is subject to variations in the mechanical condition of the door. In one embodiment, the device measures a low speed run-length over which the door has moved at a low speed. A comparator compares the measured low speed run-length with a preselected optimal low speed run-length to obtain error or departure from the optimal value. A correction logic produces an updated deceleration point by removing the error from the former deceleration point.

Abstract: Apparatus for rotating a fluid impeller of a centrifugal or axial flow fan, at multiple speeds. A fan is provided with a first and a second electric motor for drivingly rotating a fluid impeller at relatively fast and slow speeds, respectively. The rotor of the first motor directly drives the fluid impeller; the second motor is connected to the impeller shaft of the fan through a belt drive, with pulleys sized to reduce the impeller's rotational speed relative to that of the second motor.Only one of the motors is provided with a start winding. Control means selectively energize the first and second motors, and are operative to energize the one motor long enough to bring the other motor up to operating speed.

Abstract: An automatic system for controlling a plurality of motors includes motor starting circuitry and motor stopping circuitry that serves to sequentially start and stop the motors in the same cyclic order. The starting circuitry has a sensing component for sensing the presence and absence of a condition that reflects the need for starting the motor and a master starting control component which develops two different states that are used in controlling the circuits of the starting circuitry. The control circuits include a plurality of motor starting circuits for starting the respective motors and a plurality of conditioning circuits that normally respond to one of the developed states for conditioning the starting circuits for response sequentially to the other of the developed states and in a cyclic order for starting the motors.