JP6512915B2 - Control device using PWM, image forming apparatus provided with the same, and control method - Google Patents

Description

  The present invention is capable of suppressing the occurrence of overshoot and undershoot when performing deceleration control of a control target device such as a motor by PWM control adopting a feedback method, and using PWM that has high speed tracking performance. The present invention relates to an apparatus, an image forming apparatus including the same, and a control method.

  When PWM control is performed on the rotation of a motor such as a stepping motor, an output pulse of an encoder that detects the rotation of the motor is fed back to control the rotational speed and the drive amount of the motor according to a desired set amount It has been known. For example, a proportional-integral-derivative controller (PID) is used as feedback control.

  Patent Document 1 below discloses a rotation control circuit such as a spindle motor by PWM control. The rotation control circuit alternately provides a rotation drive period and a rotation deceleration period in the PWM cycle T at the time of deceleration in order to improve the followability of the motor at the time of deceleration of the rotation speed of the motor. Control. The deceleration is achieved by shorting both ends of the coil and generating a regenerative current by electromagnetic induction.

  Patent Document 2 below discloses a sheet conveying apparatus and an image forming apparatus capable of controlling (suppressing) speed fluctuation during deceleration by a simple control method. This device employs a DC brushless motor, performs powering control and braking control for each PWM cycle at the time of deceleration, and uses PID control for duty feedback. Brake control is performed by shorting the coils to form a closed loop circuit.

JP 2000-32792 A JP 2012-12186 A

  Generally, for control of a brushless motor, feedback control (for example, PID control) in which a rotational speed is detected by an encoder or the like and a detected value is fed back to calculate a control value of the motor is used. PID control is a type of feedback control in control engineering. In PID control, an input value (control value) to a control target such as a motor is divided into three values: deviation between an output value representing the state of the control target (for example, rotational speed) and a target value, integration of deviation, and differentiation of deviation. Determined by factor.

  When the PWM control of the motor is performed using the PID, the duty (Duty) of the control pulse (PWM signal) is increased at the time of acceleration and decreased at the time of deceleration to make the motor follow the target speed.

  At the time of deceleration, as disclosed in Patent Documents 1 and 2, the brake is used to decelerate. However, when the motor is rapidly decelerated using a brake, as shown in FIG. 1, there is a problem that the undershoot and the subsequent overshoot are very large and the speed tracking performance is low.

  FIG. 1 is a graph showing a state at the time of rapid deceleration of the motor by the brake (when the degree of deceleration is relatively large) in normal PID control. The upper graph shows the time change of the rotational speed (rpm) of the motor, and the lower graph shows the duty (%) of the PWM signal that controls the motor. The time axis is the same for the upper and lower graphs.

  When the motor is decelerated to a target speed X1 from a state rotating at a constant speed X0, the brake is operated at time t1 (hereinafter also referred to as ON of the brake), and the duty of the PWM signal is simultaneously made 0%. Do. This causes the motor speed to decrease rapidly. At time t2, as the target speed X1 is reached, the brake is not operated (hereinafter, also referred to as the brake OFF).

  The duty of the output (PWM signal) is basically 0% according to the PID calculation result at the time of deceleration when the brake is used. Since the PID calculation is the difference between the target value and the current value multiplied by a fixed gain, the calculation result is negative when the difference is large, and the duty of the output is fixed at 0%. Although depending on the gain used in the PID operation, in the case of slight deceleration, the duty does not naturally fall to 0%.

  Therefore, immediately after the brake is turned off, the motor can not be driven normally because the duty is 0%, and a large undershoot occurs as shown in FIG. After that, overshooting occurs when acceleration is performed from a state where the vehicle has been greatly decelerated.

  In addition, since the PID performs an accumulation operation, it takes time for the operation result to become positive even if the brake is turned off unless the negative limit is provided, and the responsiveness further decreases.

  These problems can not be solved by any of Patent Documents 1 and 2.

  Therefore, the present invention can suppress occurrence of overshoot and undershoot when decelerating controlling a control target device such as a motor by PWM control adopting a feedback method, and use PWM having high speed tracking performance. It is an object of the present invention to provide a control device, an image forming apparatus including the same, and a control method.

  The control device according to the first aspect of the present invention is a control device that controls the rotational speed of a control target by PWM control. The control device outputs, as a deviation value, a value obtained by subtracting an output value of the detection unit from a detection unit that detects and outputs the current rotation speed of the control target and a target value corresponding to the target rotation speed. Feedback unit, a PWM signal generation unit that generates a PWM signal according to an input value, and inputs the PWM signal as a control target, a reduction unit that decelerates the rotation of the control target, a feedback unit, a PWM signal generation unit, And a control unit that controls the speed reduction unit. In response to the predetermined instruction being input during a period in which the PWM signal generation unit changes the duty according to the deviation value to generate the PWM signal, the control unit causes the reduction unit to decelerate the rotation of the control target. And causes the feedback unit to output a deviation value of 0, and causes the PWM signal generation unit to generate a PWM signal of a duty according to the target value. After the control unit causes the decelerating unit to start decelerating the rotation of the controlled object, the decelerating unit receives the output value of the detecting unit becoming a predetermined value corresponding to the target value. The deceleration is stopped, and the feedback unit outputs a value obtained by subtracting the output value of the detection unit from the target value as a deviation value, and the PWM signal generation unit changes the duty according to the deviation value to generate a PWM signal Let The predetermined instruction is an instruction to make the target rotational speed smaller than the current rotational speed of the control target.

  As a result, when the rotation of the control target is decelerated, it is possible to suppress the rotational speed from undershooting and then overshooting, and it is possible to realize excellent rotational speed tracking performance.

  Preferably, the control device further includes a PID operation unit that outputs a result value obtained by performing a PID operation on the input value. The deviation value is input to the PID calculation unit instead of being input to the PWM signal generation unit, and the result value output from the PID calculation unit is input to the PWM signal generation unit, and the PWM signal generation unit The duty is changed to generate a PWM signal.

  Thus, the rotational speed of the control target can be made to quickly follow the desired rotational speed.

  More preferably, the predetermined instruction instructs the target rotational speed to be a value smaller than the current rotational speed of the control target by a predetermined value or more, or a value smaller than a predetermined ratio with respect to the current rotational speed of the control target It is an instruction.

  As a result, when the rotation of the control target is rapidly decelerated, it is possible to suppress the rotational speed from undershooting and thereafter overshooting, and it is possible to realize a good rotational speed tracking performance.

  An image forming apparatus according to a second aspect of the present invention includes the control device described above and an image forming unit for forming an image on a recording sheet. The control target is a motor used to transport the recording paper.

  As a result, in the image forming apparatus, it is possible to realize excellent recording paper conveyance control with high tracking performance.

  A control method according to a third aspect of the present invention is a control method for controlling the rotational speed of a controlled object by PWM control. This control method detects the current rotational speed of the control target and outputs it, and outputs the value obtained by subtracting the output value of the detection step from the target value corresponding to the target rotational speed as the deviation value. And a PWM signal generation step of generating a PWM signal by changing the duty according to the deviation value, and inputting the PWM signal as a control target, and a predetermined period during the generation of the PWM signal by the PWM signal generation step. In response to the instruction, the controller decelerates the rotation of the controlled object, outputs a deviation value of 0, and generates a PWM signal of a duty according to the target value. Instead of the PWM signal generated in the PWM signal generation step, the step of inputting to the control target, and after the start of deceleration of the rotation of the control target, the detection step In response to the output value becomes a predetermined value corresponding to the target value by stops deceleration of rotation of the control object, and, and performing a feedback step and a PWM signal generating step. The predetermined instruction is an instruction to make the target rotational speed smaller than the current rotational speed of the control target.

  As a result, when the rotation of the control target is decelerated, it is possible to suppress the rotational speed from undershooting and then overshooting, and it is possible to realize excellent rotational speed tracking performance.

  According to the present invention, when the rotation of a control object such as a motor is decelerated, particularly when the motor is rapidly decelerated, the rotational speed undershoots and overshooting thereafter can be suppressed, and the following performance of a favorable rotational speed can be reduced. realizable.

It is a graph which shows the state at the time of sudden deceleration in PWM control of the conventional feedback method (PID control). It is a block diagram showing a control device concerning a 1st embodiment of the present invention. It is a flowchart which shows the control structure of the program performed by the state control part of the control apparatus which concerns on 1st Embodiment. It is a graph which shows the state at the time of sudden deceleration by the control apparatus which concerns on 1st Embodiment. It is a block diagram showing a control device concerning a 2nd embodiment of the present invention. It is a flowchart which shows the control structure of the program performed by the state control part of the control apparatus which concerns on 2nd Embodiment.

  In the following embodiments, the same parts are given the same reference numerals. Their names and functions are also identical. Therefore, detailed description about them will not be repeated.

First Embodiment
Referring to FIG. 2, control device 100 according to the first embodiment of the present invention includes IF unit 102, speed detection unit 104, state control unit 106, difference generation unit 108, PID calculation unit 110, PWM generation unit And 112 and a brake control unit 114. The control device 100 controls the motor 140 to be controlled under the control of the CPU 130 of the main device (not shown) on which the control device 100 is equipped. Here, the motor 140 is a known three-phase brushless motor.

  The PID control performed in the control device 100 is not continuous time control (analog control) but discrete time control (digital control) operating with a predetermined clock. Each unit executes processing in synchronization with the input common clock.

  The IF unit 102 receives data (hereinafter, also referred to as a target value) Vtgt representing a target speed and data (hereinafter, also simply referred to as an operation mode) SD_J representing an operation mode from the CPU 130. It outputs the difference generation unit 108 and the PWM generation unit 112, and outputs the operation mode SD_J to the state control unit 106.

  The case where a value smaller than the current speed is set as the target speed of the motor 140 is referred to as a deceleration mode, and the other cases are referred to as a normal mode. The operation mode SD_J is set to “1” in the deceleration mode and to “0” in the normal mode.

  As the target value Vtgt, a value corresponding to the method of generating the PWM signal adopted by the PWM generation unit 112 is set. For example, when a PWM signal is generated using a triangular wave (including a sawtooth wave), a voltage for generating a PWM signal of a duty corresponding to the target speed is set to the target value Vtgt.

  The speed detection unit 104 generates data Vact corresponding to data ENCODE representing the current rotation state of the motor 140, which is input from the encoder 148 of the motor 140 to be controlled, and the state control unit 106 and the difference generation unit 108. Output to The encoder 148 detects the rotation of the rotor 146 of the motor 140, and outputs a pulse according to the rotation state. The encoder 148 is a known encoder (for example, an optical encoder or a magnetic encoder using a Hall element). The speed detection unit 104 includes, for example, a known FV converter (FV conversion IC), generates a voltage corresponding to an input pulse (frequency), and outputs digital data Vact corresponding thereto.

  State control unit 106 generates control data MODE in accordance with operation mode SD_J and data Vact to be input, and outputs the control data MODE to difference generation unit 108, PWM generation unit 112 and brake control unit 114.

  Here, if SD_J = 1 and Vact> Vtgt, the control data MODE is set to “1”. Otherwise, the control data MODE is set to “0”. That is, if SD_J = 0, or SD_J = 1 and Vact ≦ Vtgt, the control data MODE is set to “0”.

  The difference generation unit 108 is a difference between the target value Vtgt input from the IF unit 102 and data Vact corresponding to the rotation state of the motor 140 to be controlled, which is input from the speed detection unit 104 (hereinafter referred to as a deviation). Generate Ve (Ve = Vtgt-Vact). The output Vout of the difference generation unit 108 differs depending on the input control data MODE. That is, the difference generation unit 108 outputs “0” if MODE = 1 (deceleration mode) (Vout = 0. This corresponds to outputting the deviation Ve as “0”. MODE ≠ If 1 (MODE = 0 (normal mode)), the deviation Ve is output as it is (Vout = Ve).

  The PID operation unit 110 executes a known PID operation on the input deviation Ve. That is, a P value, an I value, and a D value are generated, and the data MV obtained by adding them is output.

  The PWM generation unit 112 operates differently depending on the input control data MODE. Specifically, if MODE = 1, the PWM generation unit 112 generates and outputs a control signal (PWM signal) PWM corresponding to the target value Vtgt. If MODE ≠ 1 (MODE = 0 (normal mode)), the PWM generation unit 112 changes the duty of the current control signal PWM in accordance with the input data MV to generate a new control signal PWM. Are output to the control IC 142 of the control device 100. For example, the control signal PWM is generated using a voltage level obtained by changing the voltage level for generating the current control signal PWM by MV. Thus, the control IC 142 controls the driver 144, which is a control circuit for controlling energization of the coil of the rotor 146, to rotate the rotor 146.

  The brake control unit 114 outputs a signal BRAKE of a level according to the input control data MODE to the control IC 142 of the motor 140. For example, the signal BRAKE is output at a high level when MODE = 1 (deceleration mode), and is output at a low level when MODE (1 (MODE = 0 (normal mode)). When the control data MODE becomes high level, the control IC 142 controls the driver 144 such that the brake is turned on. Thus, the rotational speed of the rotor 146 is reduced.

  The operation of control device 100 according to the operation mode will be described with reference to FIG. The control program shown in FIG. 3 is executed by the state control unit 106 of the control device 100. The control program is stored in a predetermined non-volatile storage device (ROM or the like, not shown) in the main device or control device, and stored by the state control unit 106 when the main device is powered on. It is read from the device and executed.

  In step 200, the state control unit 106 determines whether an operation mode command has been received from the IF unit 102. Specifically, state control unit 106 determines whether or not operation mode SD_J has been received. If it is determined that the command has been received, the control proceeds to step 202. Otherwise, step 200 is repeated.

  In step 202, the state control unit 106 determines whether the command received in step 202 represents a deceleration mode. Specifically, the state control unit 106 determines whether SD_J is "1". If SD_J = 1, it is determined that the mode is the deceleration mode, and the control proceeds to step 204. Otherwise, control transfers to step 208.

  In step 204, the state control unit 106 outputs control data MODE corresponding to the deceleration mode. Specifically, the state control unit 106 outputs “1” as the control data MODE.

  Thereby, as described above, the brake control unit 114 sets the signal BRAKE to the high level (the motor brake is turned on), and the PWM generation unit 112 controls the control signal PWM of the duty according to the target value Vtgt. Output. The output Vout of the difference generation unit 108 is “0”, and the PID operation unit 110 executes the PID operation using the input “0”.

  In step 206, the state control unit 106 determines whether to release the brake. Specifically, as described above, the state control unit 106 determines whether or not Vact ≦ Vtgt. If it is determined that Vact ≦ Vtgt, the control proceeds to step 208. Otherwise, step 206 is repeated.

  At step 208, the state control unit 106 outputs control data MODE corresponding to the normal mode. Specifically, the state control unit 106 outputs “0” as the control data MODE. Thus, the brake control unit 114 outputs the signal BRAKE at a low level. If the step 206 is executed after the step 204, the step signal BRAKE is at the high level, so it is changed to the low level (the motor brake is turned off). Otherwise, the signal BRAKE remains at low level, and the motor brake is maintained in the off state. Further, the difference generation unit 108 outputs the deviation Ve (Vout = Ve), and the PID calculation unit 110 executes the PID calculation using the deviation Ve. The PWM generation unit 112 changes the current duty according to the output MV of the PID calculation unit 110, and outputs the control signal PWM after the change. Thereafter, control returns to step 200.

  The operation at the time of rapid deceleration of the motor will be specifically described with reference to FIG. In FIG. 4, the upper graph represents the time change of the rotational speed (rpm) of the motor, and the lower graph represents the duty (%) of the control signal (PWM signal) PWM for controlling the motor. The time axis is the same for the upper and lower graphs.

  When decelerating the motor 140 from the state of rotating at a constant speed X0 to a predetermined rotation speed X1, “1” is input as an operation mode SD_J from the CPU 130 to the control device 100, and rotation is performed as a target value Vtgt Data for generating a duty corresponding to the speed X1 is input (steps 200 and 202). In response to this, the state control unit 106 sets the control data MODE to "1" (step 204). As a result, at time t1, the brake is turned on, and at the same time, the PWM signal of the duty corresponding to the designated target value Vtgt is the motor without using the PID control (without using the output value MV of the PID operation unit 110). It is output to 140. This state is maintained until the time to release the brake (time t2).

  As described above, when the brake is turned off at time t2 by inputting the PWM signal generated from the target value Vtgt to the motor 140 during time t1 to t2, the motor 140 immediately has a duty corresponding to the target speed. Since the motor is driven, as shown in FIG. 4, the rotational speed of the motor undershoots slightly, but does not undershoot as large as in the prior art (see FIG. 1). At time t2, the method of generating the control signal (PWM signal) in the PWM generation unit is switched, but no significant change occurs in the control signal PWM. At time t2, since the speed of the motor 140 is almost the target speed, the deviation is almost “0”, and the duty of the control signal PWM generated using the output MV of the PID operation unit 110 is before time t2. And the duty of the control signal PWM. Therefore, there is no large overshoot as in the prior art. As described above, the controller 100 can suppress undershoot and overshoot during rapid deceleration, and improve the follow-up performance of the rotational speed of the motor 140.

Second Embodiment
In the first embodiment, regardless of the degree of deceleration, the PWM signal is always generated during the on period of the brake regardless of the degree of deceleration regardless of PID control. On the other hand, in the second embodiment, only in the case of the rapid deceleration, the PWM signal is generated during the on period of the brake without using the PID control.

  Referring to FIG. 5, control device 300 according to the second embodiment of the present invention includes IF unit 102, speed detection unit 104, state control unit 306, difference generation unit 108, PID calculation unit 110, PWM generation unit 112 and a brake control unit 314. The control device 300 controls the motor 140 to be controlled under the control of the CPU 130 of the main device (not shown) on which the control device 300 is equipped. Here, it is assumed that the motor 140 is a three-phase brushless motor.

  The control device 300 is obtained by replacing the state control unit 106 and the brake control unit 114 with the state control unit 306 and the brake control unit 314 in the control device 100 of FIG. 1. The connection relationship between each part in the control device 300 is the same as that of the control device 100. Elements in FIGS. 2 and 5 that are given the same reference numerals perform the same operations.

  In the present embodiment, unlike the first embodiment, the deceleration is classified into two types. In the case where the current rotational speed X0 of the motor 140 is decelerated by the predetermined value Xth or more, that is, when the difference between the current speed X0 and the target speed X1 is the predetermined value Xth or more (X0−X1> Xth) It is referred to as "rapid deceleration", and in the case of performing deceleration less than a predetermined value Xth, that is, when X0-X1 <Xth is referred to as "normal deceleration". The modes corresponding to these are respectively referred to as a rapid deceleration mode and a normal deceleration mode.

  State control unit 306 generates control data MODE in accordance with operation mode SD_J and data Vact input from IF unit 102, and outputs the control data MODE to difference generation unit 108, PWM generation unit 112, and brake control unit 114. Here, if SD_J = 1 and Vact−Vtgt ≧ Vth, the control data MODE is set to “1”, and if SD_J = 1 and 0 <Vact−Vtgt <Vth, the control data MODE is “2”. It is assumed that the control data MODE is set to “0” if it is set and is otherwise. That is, if SD_J = 0, or if SD_J = 1 and Vact ≦ Vtgt, the control data MODE is set to “0”. Here, Vth is positive data corresponding to a predetermined value Xth (rotational speed).

  As described above, in the control device 300, unlike the control device 100 according to the first embodiment, “2” may be input as the control data MODE to the difference generation unit 108 and the PWM generation unit 112. However, as in the first embodiment, the difference generation unit 108 and the PWM generation unit 112 determine the operation depending on whether the control data MODE is “1”. That is, in the case of MODE = 2, the difference generation unit 108 and the PWM generation unit 112 operate in the same manner as in the case of MODE = 0.

  The brake control unit 314 outputs a signal BRAKE of a level according to the input control data MODE to the control IC 142 of the motor 140. For example, the signal BRAKE is output at a high level if MODE = 1 (sudden deceleration mode) or MODE = 2 (normal deceleration mode), and is output at a low level if MODE = 0 (normal mode). . When the control data MODE becomes high level, the control IC 142 controls the driver 144 such that the brake is turned on. Thus, the rotational speed of the rotor 146 is reduced.

  In the control device 300, the state control unit 306 executes a program shown in FIG. The flowchart of FIG. 6 is obtained by adding steps 400 and 402 to the flowchart of FIG. 3. In FIG. 3 and FIG. 6, the processes in the steps given the same reference numerals are the same.

  The operation of control device 300 according to the operation mode will be described with reference to FIG. The control program is stored in a predetermined non-volatile storage device (ROM or the like, not shown) in the main device or control device 300, and the power of the main device is turned on. It is read from the storage device and executed.

  When a deceleration command is input from the CPU, in step 400, the state control unit 306 determines whether or not the command received in step 202 represents a rapid deceleration mode. Specifically, the state control unit 306 determines whether the condition of SD_J = 1 and Vact−Vtgt ≧ Vth is satisfied. If this condition is satisfied, it is determined that the rapid deceleration mode is in effect, and the control proceeds to step 204. Otherwise (SD_J = 1 and 0 <Vact−Vtgt <Vth), the control proceeds to step 402.

  In the case of the rapid deceleration mode, steps 204 to 208 are performed as in the first embodiment, and then the control returns to step 200.

  On the other hand, in the case of the normal deceleration mode, in step 402, the state control unit 306 outputs "2" as the control data MODE. Thereby, as described above, the brake control unit 314 sets the signal BRAKE to the high level (the brake of the motor is turned on). The difference generation unit 108 outputs the deviation Ve (Vout = Ve), and the PID calculation unit 110 executes the PID calculation using the deviation Ve. The PWM generation unit 112 changes the current duty of the control signal PWM according to the output MV of the PID calculation unit 110, and outputs the control signal PWM after the change. Thereafter, steps 206 and 208 are performed.

  As described above, in the case of the normal deceleration mode, the same braking operation as that in the past is performed in steps 402, 206 and 208. Since this is not a rapid deceleration, the large undershoot and overshoot as shown in FIG. 1 do not occur. Further, at the time of rapid deceleration, as in the first embodiment, step 204, step 206 and step 208 are executed, so undershoot and overshoot are suppressed as shown in FIG.

  Some motors can not be turned off immediately once the brake is turned on. Therefore, in the case of the control device 100 of the first embodiment, if the degree of deceleration is small, the brake is applied more than necessary. It can happen that it decreases more than the speed (occurrence of undershoot). On the other hand, in the control device 300, when the degree of deceleration is small, the conventional deceleration control is performed, and therefore, the speed does not decrease much more than the target speed.

  In the second embodiment described above, the deceleration equal to or greater than the predetermined value is the rapid deceleration, but it is optional what kind of deceleration should be the rapid deceleration. In the case where the target velocity is set to a predetermined ratio or less with respect to the current velocity, the rapid deceleration may be performed. Also, the conditions for the rapid deceleration may be determined by combining the current speed and the target speed, their difference, their ratio, and the like. For example, when the motor rotation speed is decelerated from 2000 rotations or more to 800 rotations or less is taken as rapid deceleration, and when decelerating from 1000 rotations, it may be taken as normal deceleration.

  Although the case where the state control unit 306 determines whether or not the rapid deceleration mode is determined has been described in the second embodiment described above, the present invention is not limited to this. The CPU 130 may determine whether or not the rapid deceleration mode is set, and may input the operation mode SD_J of data according to the determination result to the control device 300. For example, SD_J = 0 in the normal mode, SD_J = 1 in the rapid deceleration mode, and SD_J = 2 in the normal deceleration mode. In that case, the state control unit 306 can determine the control data MODE according to the operation mode SD_J.

  In the first and second embodiments described above, although the case where PID control is performed in PWM control has been described, the present invention is not limited to this. In PWM control, what is necessary is just to use feedback control. The output Vout of the difference generation unit 108 may be input to the PWM generation unit 112 without the PID calculation unit 110.

  In the first and second embodiments described above, the case has been described where the PWM signal generated by the PWM generation unit is input to the motor 140 without using PID control in the on period of the brake. I will not. Some motors ignore the input of the PWM signal while the brake is on. When controlling such a motor, it is not necessary to input a PWM signal generated without PID control to the motor. However, the PWM generation unit maintains the generation of the dummy PWM signal during the on period of the brake.

  In the first and second embodiments described above, the timing at which the brake is turned off after the brake is turned on is the time when the target speed is reached, but it is not limited to this. For example, the brake may be turned off when the current speed reaches a value slightly larger than the target speed. That is, if Vact-Vtgt ≦ α is satisfied, the brake is turned off. α is a value set appropriately.

  In the above first and second embodiments, after the brake is turned on, the timing to turn off the brake is determined using the detected value of the rotational speed of the motor, but it is not limited to this. It may be determined whether the rotational speed of the motor has reached the target value based on the passage of time. For example, if the rotation speed of the motor to be used is limited (for example, when used at several fixed speeds), the predetermined time required for deceleration is set in advance, and the predetermined time has elapsed since the brake was turned on. When the target speed is reached, the brake may be turned off (MODE is set to “0”).

  Although the case where the CPU 130 is disposed outside the control device 100 or 300 has been described in the above first and second embodiments, the present invention is not limited to this. The CPU 130 may be disposed inside the control device 100 or 300.

  Although the case where the motor 140 is a three-phase brushless motor has been described above, the present invention is not limited to this. It may be any device driven by PWM control.

  The present invention can be applied to an image forming apparatus (typically, a copier) that forms an image on a recording sheet. Various motors are used in the image forming apparatus. For example, the image forming apparatus includes a motor for driving a roller for conveying the recording sheet pulled out of the cassette, and the control device 100 or 300 can be used to control the motor.

  The present invention has been described above by describing the embodiment, but the above-described embodiment is an exemplification, and the present invention is not limited to the above-described embodiment, and various modifications may be made. be able to.

100, 300 Control unit 102 IF unit 104 Speed detection unit 106, 306 State control unit 108 Difference generation unit 110 PID operation unit 112 PWM generation unit 114, 314 Brake control unit 130 CPU
140 Motor 142 Control IC
144 Driver 146 Rotor 148 Encoder

Claims (5)

A control device for controlling a rotational speed of a control target by PWM control,
Detection means for detecting and outputting the current rotational speed of the control object;
Feedback means for outputting a value obtained by subtracting the output value of the detection means from a target value corresponding to a target rotational speed as a deviation value;
PWM signal generation means for generating a PWM signal according to an input value and inputting the PWM signal to the control target;
Decelerating means for decelerating the rotation of the controlled object;
The feedback means, the PWM signal generation means, and a control means for controlling the speed reduction means,
The control means receives that a predetermined instruction is input during a period in which the PWM signal generation means changes the duty according to the deviation value to generate the PWM signal,
Causing the decelerating means to start decelerating the rotation of the controlled object;
Causing the feedback means to output the deviation value to 0,
Causing the PWM signal generation unit to generate a PWM signal of a duty according to the target value;
The control means receives the output value of the detection means becoming a predetermined value corresponding to the target value after having the deceleration means start reducing the rotation of the controlled object.
Causing the decelerating means to stop decelerating the rotation of the controlled object;
Causing the feedback means to output a value obtained by subtracting the output value of the detection means from the target value as the deviation value.
Causing the PWM signal generation unit to generate a PWM signal by changing the duty according to the deviation value;
The control device, wherein the predetermined instruction is an instruction to make the target rotational speed smaller than a current rotational speed of the control target. Further including PID operation means for outputting a result value obtained by performing a PID operation on the input value;
The deviation value is input to the PID operation means instead of being input to the PWM signal generation means.
The result value output from the PID calculating unit is input to the PWM signal generating unit;
The control device according to claim 1, wherein the PWM signal generation unit changes a duty according to the result value to generate a PWM signal.   The predetermined instruction instructs the target rotational speed to be a value smaller than the current rotational speed of the control target by a predetermined value or more, or sets the target rotational speed to a value smaller than a predetermined ratio with respect to the current rotational speed of the control target. The control device according to claim 1, which is an instruction. The control device according to any one of claims 1 to 3.
And image forming means for forming an image on a recording sheet,
The image forming apparatus, wherein the control target is a motor used to transport the recording sheet. A control method for controlling the rotational speed of a controlled object by PWM control, comprising:
A detection step of detecting and outputting a current rotational speed of the control target;
A feedback step of outputting a value obtained by subtracting an output value of the detection step from a target value corresponding to a target rotational speed as a deviation value;
A PWM signal generation step of changing a duty according to the deviation value to generate a PWM signal, and inputting the PWM signal to the control target;
During a period in which the PWM signal is generated by the PWM signal generation step, in response to a predetermined instruction being made, deceleration of the rotation of the control target is started, and the deviation value is set to 0 and output. And generating a PWM signal of a duty according to the target value and inputting the PWM signal to the control target instead of the PWM signal generated in the PWM signal generation step;
After starting to decelerate the rotation of the controlled object, the decelerating of the controlled object is stopped in response to the output value by the detection step becoming a predetermined value corresponding to the target value, and Performing a feedback step and the PWM signal generation step;
The control method, wherein the predetermined instruction is an instruction to make the target rotational speed smaller than a current rotational speed of the control target.

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