Abstract: A clock signal generation circuit includes: a triangular wave generation circuit configured to generate a triangular wave signal; a pseudo-random number generation circuit configured to generate a pseudo-random number signal; a limiter circuit configured to perform a limitation process of limiting an amount of change per unit time in the pseudo-random number signal and generate the pseudo-random number signal subjected to the limitation process as a limiter signal; a linear arithmetic circuit configured to generate a frequency control signal by performing a linear arithmetic operation on the triangular wave signal and the limiter signal; and an oscillator configured to generate a clock signal having a frequency corresponding to the frequency control signal.

Abstract: A machine tool includes three mutually independent data transmission mechanisms. The data transmission mechanisms include respective transmission units which assign codes for detecting errors to data acquired from the output of sensors, and which transmit the data. A machine controller includes an operation judgment unit which judges whether operation of a feed axis motor is continued. The operation judgment unit judges that operation is continued when there are two pieces of data for which a relationship between the data and the code matches a rule, and the two pieces of data are within a predetermined judgment range. The operation judgment unit judges that the feed axis motor is stopped when at least one of the pieces of data for which the relationship matches the rule deviates from the judgment range.

Abstract: In some examples, an alternator control device includes interface configured to receive a voltage signal from an engine control device, pull-down circuitry, and a switch electrically connected between the interface and the pull-down circuitry. The alternator control device further includes processing circuitry configured to determine that the voltage signal is higher than a threshold voltage level and to activate the switch to electrically connect the interface to the pull-down circuitry in response to determining that the voltage signal is higher than the threshold voltage level. The processing circuitry is further configured to determine that, at least a threshold time duration after activating the switch, the voltage signal is higher than the threshold voltage level and to refrain from delivering the excitation current based on determining that, at least the threshold time duration after activating the switch, the voltage signal is higher than a threshold voltage level.

Abstract: A controlling circuit for outputting a square wave circuit to control a fan rotating speed is disclosed, where an output unit continuously outputs the square wave signal and the output unit is electrically connected to a time-delaying adjustment circuit, so that a duty-ratio formed not equal to 50% is outputted to control the fan rotating speed, whereby a particular duty-ratio is provided to control the fan rotating speed after a control chip for fan rotating speed is pulled out.

Abstract: A data reception unit carries out reception of data, which consists of a combination of switching noise resistant states and switching noise nonresistant states, over a fixed serial communication time a plurality of times for each fixed serial communication period same as the one or a plurality of the switching periods. A serial communication time setting unit sets the serial communication time different from one or a plurality of the switching periods, based on the switching period, the serial communication period, and the communication speed of the data communication device, so that the starts of all of the switching periods within the serial communication time are consistent with the time of reception of the switching noise resistant state at the time of at least one of the reception of the data among a plurality of times of the reception of the data.

Abstract: A method for activating a jamming protection function in an electrical closing system. The jamming protection function is designed to abort a movement of a closing part in a movement direction if it is detected that the movement of the closing part is obstructed by a jammed object by: —providing consecutively measured values of a motor variable of a motor that effect the movement of the closing part, wherein the motor variable gives an indication of a drive torque provided by the motor; —determining a gradient curve from the consecutively measured values of the motor variable, wherein the gradient curve is established using a derivative method that provides for a weighting of the individual consecutively measured values of the motor variable according to the measurement sequence thereof; —establishing a point in time for activating the jamming protection function according to the determined gradient curve.

Abstract: A vehicle door opening-closing apparatus is provided, which includes a vibration detector and a controller. The controller acquires an envelope formed by connecting crests or troughs of a waveform of vibration detected by the vibration detection sensor. The controller determines whether or not a shape of the envelope meets a condition. A vehicle door is controlled based on a result of determination by the controller.

Abstract: A motor control device includes a sensing circuit, a phase-shifting circuit, a comparing circuit and a control circuit. The sensing circuit senses the motor to generate a sensing signal. The phase-shifting circuit is electrically connected to the sensing circuit and receives the sensing signal to generate a phase-shifting signal. The comparing circuit is electrically connected to the phase-shifting circuit and receives the phase-shifting signal to generate a comparing signal. The control circuit is electrically connected with the comparing circuit and the motor, and receives the comparing signal to generate a control signal so as to control the rotation speed of the motor.

Abstract: An on-vehicle charging apparatus charges a battery mounted on the vehicle. In the apparatus, a generator generates electric power to output voltage for charging the battery and a controller, which is located outside the generator, outputs a pulse signal for controlling a generated state of the generator. A reception device receives the pulse signal outputted from the controller. The received signal is subjected to filtering at a filter, where pulse signals whose cycles are different from a predetermined cycle are removed. Further, using the outputted pulse signal from the filter, a duty ratio of the pulse signal is calculated. A voltage outputted from the generator is regulated based on the calculated duty ratio.

Abstract: A motor driver system includes an inverter configured to apply a three-phase voltage to a motor; an inverter driver configured to generate a reference voltage to the inverter to control a motor speed to follow a reference speed; and a motor protector configured to control the inverter driver so that a value of the reference voltage is equal to or lower than a predetermined voltage value.

Abstract: An electric motor drive control method includes deriving a target current from a target torque to apply electric current corresponding to the target current to an electric motor. When a rotation speed of the motor is in a predetermined speed region, including a zero rotation speed at which the target current for driving the motor allocated to the target torque is switched discontinuously, the target current corresponding to the rotation speed is obtained through a linear interpolation using the rotation speed and target currents at a traction side and a regeneration side allocated to the target torque such that the electric current corresponding to the target current is applied to the motor.

Abstract: A controlling device includes a range switch mechanism, range switch operating means, operation frequency monitoring means, and heat generation limit controlling means. The range switch mechanism is adapted to change a shift range using a motor. Through the range switch operating means, an occupant inputs a required shift range. The motor is controlled in accordance with the required shift range such that the shift range is changed into the required shift range. The operation frequency monitoring means monitors an operation frequency of the range switch operating means. The heat generation limit controlling means switches a control of the motor to a heat generation limit control when the operation frequency of the range switch operating means exceeds a predetermined frequency.

Abstract: Controlling and adjusting of the operation of a device actuated by an electric motor are carried out by shutting down the electric power supply of said electric motor at a plurality of time intervals during the motor operation, measuring in the time interval the voltage supplied by the electric motor, comparing the value of the measured voltage with a reference value and, if required on the basis of said comparison, varying at least one parameter related to the functioning of the device in order to compensate possible deviations.

Abstract: The rotational speed of a motor is detected, and stored in a rotational speed memory. The difference between the present rotational speed output and each of plural past rotational speeds stored in the rotational speed memory is calculated in a plural difference calculator. Whether the difference between the present rotational speed and the most past rotational speed out of the plural differences is larger than a first threshold value is judged. Whether at least one of the differences is larger than a second threshold value is judged. The first and second threshold values are set to values for detecting that the rotational speed of the motor has a decelerating trend through the comparison with the differences concerned, and the first threshold value is set to be smaller than the second threshold value. When both judgments have positive judgment results, it is judged that rotation abnormality of the motor occurs.

Abstract: A motor driver system includes an inverter configured to apply a three-phase voltage to a motor; an inverter driver configured to generate a reference voltage to the inverter to control a motor speed to follow a reference speed; and a motor protector configured to control the inverter driver so that a value of the reference voltage is equal to or lower than a predetermined voltage value.

Abstract: The invention relates to a temperature tripping device for reliably shutting down a load, especially a motor, having at least one input for receiving at least one temperature-dependent sensor signal as an input signal, a first evaluation circuit for generating a first output signal if the input signal reaches a preset value, and means for generating a trip signal if the output signal is generated. In addition, a second, redundant, evaluation channel is provided which is supplied with the same input signal as the first evaluation channel and which generates a second output signal if the input signal reaches the preset value, wherein the means for generating a trip signal are connected to the two evaluation channels and generate the trip signal if at least one of the two output signals is generated.

Abstract: This seatbelt apparatus includes: a belt reel around which a belt is wound; a motor which rotationally drives the belt reel; a transmitting device which transmits a driving power between the belt reel and the motor; a controller which drives the motor while controlling an electricity to be supplied to the motor; a rotation-detection device which detects a rotation status of the belt reel. The rotation-detection device outputs, in accordance with a rotation of the belt reel, a plurality of outputs including signals indicating a first state in which a current consumption by the rotation-detection device is larger than a predetermined value, and a second state in which the current consumption by the rotation-detection device is smaller than the predetermined value. The controller executes a first motor-driving process in which the motor is driven based on an output from the rotation-detection device until reaching the second state.

Abstract: An angle computing section determines an angle of a rotor, and an angular velocity computing section determines angular velocity of the rotor. A command current computing section determines, from a steering torque and vehicle velocity, command currents and taken along d-q axes. An open loop control section determines, from command currents and angular velocity, command voltages taken along the d-q axes in accordance with motor circuit equations. A d-q axis/three-phase conversion section converts the command voltages into command voltages of three phases. A ? computing section determines the number of armature winding flux linkages included in a motor circuit equation from a q-axis command voltage, the current value detected by a current sensor, and the angular velocity. Circuit resistance including armature winding resistance R included in the motor circuit equation may also be determined by means of the same configuration.

Abstract: Controlling and adjusting of the operation of a device actuated by an electric motor are carried out by shutting down the electric power supply of said electric motor at a plurality of time intervals during the motor operation, measuring in the time interval the voltage supplied by the electric motor, comparing the value of the measured voltage with a reference value and, if required on the basis of said comparison, varying at least one parameter related to the functioning of the device in order to compensate possible deviations.

Abstract: A microcomputer (an electric current command value calculating section) carries out field weakening control in which a d-axis electric current command value Id* is set to a negative value in correspondence with rotation angular velocity ? of a motor. The microcomputer determines whether an anomaly has occurred in an EPS. If it is determined that an anomaly is in a power supply system (step 202: YES), the microcomputer determines whether the anomaly in the power supply system is failure of electric current flow in any phase (step 203). If it is determined that electric current flow has failed in a certain phase, the microcomputer prohibits the field weakening control and outputs a motor control signal instructing to use two other phases free from the failure of electric current flow as electric current flowing phases (two phase drive mode, step 204).

Abstract: The invention relates to a windscreen wiper, comprising a protection device for the electric motor for the drive thereof and corresponding method. The windscreen wiper comprises a DC motor (2) with first, second and third carbon contacts (10, 14, 40) rubbing on the rotor thereof. The first carbon contact (10) is the earth, the second is selectively connected to a DC current supply (17) and the third is connected to neither the earth nor the DC current supply (17). A sub-assembly for detection of sticking of the electric motor (2) provides information on the sticking of the motor. Voltage measuring means between the first and the third carbon contacts (10, 40) permit the taking of a first measured voltage value which is compared to a first threshold value to generate further second information on the sticking of the electric motor (2) if said voltage is lower than the first threshold value.

Abstract: A washing machine having balancers and a method of controlling the same is provided. The number of rotations of a motor is maintained at a designated number before excessive vibration of a tub occurs for a designated time in order to prevent excessive vibration of the tub before balls reach a balancing position. The method includes sensing the number of rotations of a motor; determining whether or not the sensed number of rotations of the motor reaches a designated number of rotations by comparing the sensed number of rotations of the motor with the designated number of rotations; and controlling the motor such that the number of rotations of the motor is maintained at the designated number of rotations when it is determined that the sensed number of rotations of the motor reaches the designated number of rotations.

Abstract: An electric motor drive control method includes deriving a target current from a target torque to apply electric current corresponding to the target current to an electric motor. When a rotation speed of the motor is in a predetermined speed region, including a zero rotation speed at which the target current for driving the motor allocated to the target torque is switched discontinuously, the target current corresponding to the rotation speed is obtained through a linear interpolation using the rotation speed and target currents at a traction side and a regeneration side allocated to the target torque such that the electric current corresponding to the target current is applied to the motor.

Abstract: An air cleaner is provided according to an embodiment of the invention. The air cleaner includes a volatile memory including an air cleaner state memory element and a non-volatile memory including an air cleaner state backup memory element. The air cleaner is configured to store an air cleaner state to the air cleaner state memory element of the volatile memory and store the air cleaner state to the air cleaner state backup memory element of the non-volatile memory.

Abstract: The invention concerns a sequential safety system associated with a moving closing panel driven so as to slide by an electric motor (6), this safety system including means (20) exploiting the signal originating from an optical fiber to stop and reverse the direction of movement of said moving panel in the event of a change in the signal, as well as additional safety means allowing the end-of-travel positions of the moving panel to be determined without ambiguity via the joint exploitation of the results derived from measuring the frequency of the pulses caused by the rotation of the electric motor (6) driving said moving panel, as well as data originating from the optical fiber.

Abstract: The invention relates to a circuit and a method for the speed control of a d.c. motor, particularly the speed control of a fan driven by this d.c. motor, which is used as part of an air distribution system in passenger and commercial motor vehicles. The circuit for the speed control of a d.c. motor includes, according to the invention, a d.c. motor and a supply voltage supplying this d.c. motor, a control module for the generation of PWM-signals and registration of measurement currents and measurement voltages, a number n of parallel-connected field effect transistors which are designed suppliable with PWM-signals in a cascade manner to switch the d.c. motor, and a number n?1 resistors which are designed each to be connected with one of the n field effect transistors which are designed each to be connected with one of the n field effect transistors, whereby n is at least 2.

Abstract: A brushless motor driving device having a current detecting unit for detecting a phase-current of a brushless motor, a voltage detecting unit for detecting a phase voltage of the brushless motor, and a signal input portion to which the detection value of the phase-current and the detection value of the phase-voltage are input and which has plural input terminals arranged sequentially. The detection values of phase currents or detection values of phase voltages which are different in characteristic are input to adjacent input terminals.

Abstract: A master controller installed in a master controller box and slave controllers installed in car doors to open and close window glasses of a car are connected by a single wire to each of slave controllers for enabling to send control signals through such a single wire so that the master controller applies DOWN current signal, UP current signal and no flow of current to slave controllers.

Abstract: A drive for a vehicle HVAC vent door includes a drive transmission mounted within the shaft for the vent door. The drive transmission is of the sort commonly known as a wave drive transmission, wherein a lobed member is driven by an oblong drive shaft. The lobed member selectively drives an externally threaded flex ring that in turn engages an internally toothed drive transmission member. The internally toothed drive transmission member drives the shaft for the vent door. In this fashion, a relatively small motor is provided which has sufficient power to drive the vent door. Further, an electrical connection for supplying control signals is mounted at one end of the shaft and has a non-symmetrical configuration such that the motor and vent door will be properly orientated and relative to the vehicle.

Abstract: An opening and closing control device of opening and closing member for a vehicle includes a motor for actuating the opening and closing member, and a control unit for driving the motor so as to become a predetermined target speed and for driving the motor in reverse direction as a detection of entrapped obstacles when the actual speed of the motor reaches to an entrapment judgment speed which is set lower than the target speed. The control unit sets a threshold speed which is higher than the target speed and outputs an output duty to the motor for achieving the target speed by feedback control. The control unit switches the output duty after the actual speed of the motor becomes higher than the threshold speed to an output by feedforward control based on the target speed.

Abstract: An induction actuated container includes a container body, a container cover, a drive and an induction element. The drive includes a driven operating member and a driving member. The induction elements includes a sensor and an actuating controller for the driving member. One end of the driven operating member is transmissively connected with the container cover, the other end is transmissively connected with the driving member, and the sensor is electrically connected with the actuating controller for the driving member, and the actuating controller for the driving member is connected with a controlling end of the driving member. A signal caused by the approaching of a human or object is received by the sensor and is converted into an electrical signal. Then, the actuating controller for the driving member controls the driving member to perform a corresponding mechanical action.

Abstract: A wiper device for a window, in particular in a motor vehicle, including a wiper blade, a mechanical system that drives the wiper blade, and a control device that compensates for the clearances of the mechanical system as a function of load changes and/or as a function of service life and a method for operating such a wiper device.

Abstract: An open-loop system for synchronizing movement of a slide out room includes a pair of motors connected to extendable members which support the room during movement between an extended and a retracted position for driving the extendable members, a controller connected to the motors, and a plurality of switches connected to the controller for permitting operator control of the system. The controller provides synchronized output signals to the motors which have known output characteristics depending upon the motor inputs. The controller thus ensures the motors move substantially in unison without requiring feedback from the motors or the extendable members. The system may be initialized to establish stop positions of the extendable members which are stored in the controller.

Abstract: An entrapment detection device of an opening/closing member which efficiently performs an entrapment determination and restrains an entrapment load even when a motor rotational signal is not inputted. The entrapment detection device includes a controller for performing the entrapment detection based on detected motor rotational signal cycle changes outputted from a motor rotation sensor which is synchronized with the movement of a motor for actuating an opening/closing member. The controller stores the cycle changes of a predetermined number of output pulses from the sensor, predetermines a standard cycle time Tb from the stored pulse output, and calculates a cycle coefficient of the entrapment. When the motor rotational speed is reduced, an entrapment detection operation is performed by comparing a value of time from a previous cycle change to a current cycle change multiplied by the calculated cycle coefficient with the standard cycle Tb.

Abstract: A movable barrier operator includes a wall control switch module having a learn switch thereon. The switch module is connectable to a control unit positioned in a head of a garage movable barrier operator. The head unit also contains an electric motor which is connected to a transmission for opening and closing a movable barrier such as a garage door. The switch module includes a plurality of switches coupled to capacitors which, when closed, have varying charge and discharge times to enable which switch has been closed. The control unit includes an automatic force incrementing system for adjusting the maximal opening and closing force to be placed upon the movable barrier during a learn operation. Likewise, end of travel limits can also be set during a learn operation upon installation of the unit.

Abstract: An apparatus invention relates to an apparatus and method for monitoring an interior space which is closed off by a locked and/or manually non-unlockable door, flap, sliding sunroof or the like, for example a passenger compartment or luggage compartment of a motor vehicle, with respect to living entities enclosed therein and the quality of their living environment, having a control circuit and sensor evaluation arrangements connected thereto, which arrangements each interact with at least one sensor, a first sensor evaluation arrangement outputting a first signal to the control circuit if there are living entities in the interior space, and a second sensor evaluation arrangement outputting a second signal to the control circuit if the living environment changes in the direction of life- and/or health-threatening states, at least one actuator connected to the control circuit acting on a motor-actuatable closure of the door, flap, sliding sunroof or the like, which is activated by the control circuit for the pu

Abstract: The present invention relates to a trapping protector capable of detecting the presence of an object in a sensing region when connected with a device for creating input signals and evaluating output signals. Said trapping protector comprises a body portion, at least one ground electrode, at least one sensor electrode arranged spaced apart from said ground electrode and embedded in said body portion, and a zone of reduced rigidity between said at least one ground electrode and said at least one sensor electrode. Said zone reduces the force required for triggering said trapping protector.

Abstract: A squeeze protection system for movable parts of a vehicle, includes an operating switch for one or several parts to be moved, one or several actuators assigned to the operating switch, a control device for the actuator or the actuators which receives a signal from the operating switch, and a device for determining an irregularity during the movement of the movable part which device is coupled with the control device. In order to ensure a secure closing of the movable part also in the event of an operating disturbance, it is provided that, when the operating switch is activated and an irregularity is detected during the movement of the movable part, the movement is first interrupted and is then continued at a higher switch-off threshold.

Abstract: A pair of capacitors are provided at a window sash or a window glass edge. Each capacitor is connected to two variable phase delay generators in parallel. Selectors are inserted between the capacitors and variable phase delay generators. Each selector alternates the connection between the capacitor and two variable phase delay generators. Upon insertion of human bodies, two variable phase delay generators reverse relative phase delays of the output signal from the two variable phase delay generators. If one of the relative phase delays is reversed, the human bodies are detected to be inserted into the window opening.

Abstract: The invention includes: a random number generating unit which outputs a random number in driving of an AC motor by a voltage source inverter, a maximum/minimum triangular wave frequency setting unit which calculates a maximum triangular wave frequency and minimum triangular wave frequency using the inverter frequency, a triangular wave frequency calculating unit which calculates a triangular wave frequency from the random number, the maximum/minimum triangular wave frequency, and a triangular wave peak pulse, a triangular wave generating unit which calculates a triangular wave in accordance with this triangular wave frequency and outputs a triangular wave peak pulse, a voltage reference generating unit which inputs inverter current references and the motor revolution frequency, and which calculates the inverter frequency and voltage references of each phase of the inverter, and a PWM pulse generating unit which inputs the voltage references and triangular wave of each phase which are calculated and outputs a

Abstract: An electric motor drive for an automotive operating element for moving between at least two end positions. A range about at least one selected position of the operating element is established. The drive automatically moves the operating element into the selected position when the automotive operating element has reached the established range.

Abstract: In an opening/closing member driving method in which the rotation of a motor rotatable in two directions is transmitted through a transmission member to an opening/closing member to thereby drive a baffle 4 in an opening direction A and in a closing direction B, when driving the transmission member from an intermediate position to an original position which is set at a position where the transmission member is moved to the full in one direction or in the other direction, the transmission member is once driven in the opposite direction to the original position and is stopped at such opposite position or in the neighborhood of the opposite position and, after then, the transmission member is driven in the original position direction by an amount equivalent to the normal movement thereof and is thereby returned to the original position.

Abstract: In a method of starting rotation of a magnetic disk medium of a large-capacity flexible disk by a spindle motor for use in a high-density type flexible disk drive for carrying out data recording and reproducing operation to and from the magnetic disk medium of the large-capacity flexible disk which requires to rotate at a high rotation speed on recording and reproducing, the method includes: a first step of rotating the spindle motor at a low rotation speed lower than the high rotation speed on rotation starting of the magnetic disk medium; a second step of rotating the spindle motor at the high rotation speed subsequently to rotating of the spindle motor at the low rotation speed; a third step of rotating the spindle motor at the low rotation speed subsequently to rotating of the spindle motor at the high rotation speed; and a fourth step of rotating the spindle motor at the high rotation speed subsequently to rotating of the spindle motor at the low rotation speed at the third step.

Abstract: A power closure panel control apparatus is independent of closure panel configuration and capable of a diverse range of remote and direct activation. Sophisticated safety features utilize an adaptive strategy to facilitate highly sensitive obstruction detection by learning the closure system's force requirement and applying a safety margin to it. The control system allows the closure panel to operate in a totally manual mode.

Abstract: A control system for an electric vehicle includes an accelerator opening detecting device for detecting a position of an accelerator, and an output command value calculating device connected to the accelerator opening detecting device for calculating an output command value of a drive motor of the electric vehicle based upon the detected accelerator opening. A motor control device is connected to the output command value calculating device, and controls the output of the motor based upon the output command value. An accelerator opening learning device learns actual accelerator opening positions, and includes at least one of a full-closure learning apparatus for generating a full-closure determined value of the accelerator based upon an output of the accelerator opening detecting device, and a full-open learning apparatus for generating a full-open determined value based upon the detected accelerator opening.

Abstract: An absolute angular position calculator for a rotating motor and a velocity control apparatus adopting the same, in which a separate pulse generator is not used. The motor is manufactured so that a modified frequency generator generates a modified frequency signal by removing one pulse from the predetermined number of pulses of a frequency signal, by changing a duty of one pulse of the frequency signal, or by changing a magnitude of the frequency signal. When the motor is in use, a modification point of the frequency signal is detected to produce an absolute angular position which is used for producing a disturbance correction value, via learning, to be stored. Velocity control is performed using the stored disturbance correction value.

Abstract: A method for monitoring the condition of electrical-motor-driven devices. The method is achieved by monitoring electrical variables associated with the functioning of an operating motor, applying these electrical variables to a three phase equivalent circuit and determining non-symmetrical faults in the operating motor based upon symmetrical components analysis techniques.

Abstract: A device for detecting the stop of a stepping-motor-operated damper for a refrigerator, the damper having a stepping motor, a baffle driven by the stepping motor, a rotation control unit for controlling the direction of rotation and the amount of rotation of the stepping motor. The device includes a memory unit for storing a set value for detecting a position where the baffle is stopped, a measuring unit for measuring an electrical drive signal provided when the baffle is being driven, a comparison unit for comparing the electrical drive signal with the set value, and a stop detecting unit for determining that the baffle has been stopped when the comparison unit determines that the electrical drive signal is larger than the set value, to output a stop signal.

Abstract: An apparatus for controlling a load lifting implement of a work vehicle in response to the condition of a motor brush is provided. The vehicle has a frame and the load lifting implement is connected to the frame and elevationally moveable relative to the frame between first and second directions. A brush wear indicator senses the wear of the motor brush and produces a warning signal in response to a predetermined amount of wear of the motor brush. A control system receives the warning signal and responsively controllably inhibits the elevational movement of the load lifting implement in at least one of the first and second directions.

Abstract: A concentration of a given gas is detected by a gas sensor when a command signal for turning off the gas sensor is present, the concentration is stored and the gas sensor is turned off. The invention detects the concentration of the given gas by the gas sensor when a command signal for turning on the gas sensor is present and determines a reference value by choosing either the stored concentration or the concentration detected after the gas sensor is turned on whichever is lower at an instant a predetermined interval after the gas sensor is turned on. A blower motor of an air cleaner is controlled in accordance with the difference between the reference value and the concentration detected after the gas sensor is turned on. In a second method, the concentration is stored in a nonvolatile memory just before the air cleaner is turned off. In a third method, a given value may be set as the reference value replacing the stored concentration if the given value is smaller than the stored concentration.