Actuator control device and actuator control method

Abstract

In one aspect of an actuator control device and an actuator control method according to the present invention, an actuator using a motor is controlled by a control device, and when the load of the actuator or the processing load of the control device is high, the number of feedback control loops used in controlling the motor is reduced compared to when the load of the actuator or the processing load of the control device is low. Thus, even if the load of the actuator or the processing load of the control device increases, it is possible to prevent the trackability of the control amount with respect to the target value from worsening.

Description

Actuator control device and actuator control method

[0001] The present invention relates to an actuator control device and an actuator control method.

[0002] The variable valve timing device of Patent Document 1 controls the intake valve phase after an engine stop command is issued, with the stop phase as the target value, and selects the fastest mode in which the power supplied to the electric motor (actuator) is fixed at the maximum value until a mode switching condition is met.After that, when the intake valve phase approaches the stop phase and the mode switching condition is met, the control mode is switched from the fastest mode to the normal mode, and feedback control of the intake valve phase is performed.

[0003] Japanese Patent Application Laid-Open No. 2008-057351

[0004] In an actuator that uses a motor, such as an electric variable valve timing mechanism, feedback control using multiple feedback control loops is sometimes performed. However, in the case of such feedback control using multiple feedback control loops, control delays are likely to occur as the load on the actuator and the processing load on the control device increase, and the ability of the controlled variable to follow a target value may deteriorate.

[0005] The present invention has been made in consideration of the current situation, and its purpose is to provide an actuator control device and an actuator control method that can prevent a deterioration in the ability of a control variable to track a target value, even if the load on the actuator or the processing load on the control device increases.

[0006] Therefore, one aspect of the actuator control device according to the present invention is an actuator control device that controls an actuator that uses a motor, and reduces the number of feedback control loops used to control the motor when the load on the actuator or the processing load of the control device is large, compared to when they are small. Also, one aspect of the actuator control method according to the present invention is an actuator control method that controls an actuator that uses a motor by a control device, and includes a step of reducing the number of feedback control loops used to control the motor when the load on the actuator or the processing load of the control device is large, compared to when they are small.

[0007] According to the above invention, even if the load on the actuator or the processing load on the control device increases, it is possible to prevent the ability of the controlled variable to follow the target value from deteriorating.

[0008] 1 is a diagram showing an internal combustion engine for a vehicle; FIG. 2 is a block diagram showing a control system for a VVT mechanism; FIG. 3 is a flowchart showing a first embodiment of a control process for a VVT mechanism; FIG. 4 is a time chart for explaining the operation and function of the first embodiment; FIG. 5 is a flowchart showing a second embodiment of a control process for a VVT mechanism; FIG. 6 is a flowchart showing a third embodiment of a control process for a VVT mechanism; FIG. 7 is a flowchart showing a fourth embodiment of a control process for a VVT mechanism; FIG. 8 is a flowchart showing a fifth embodiment of a control process for a VVT mechanism; FIG. 9 is a time chart for explaining the operation and function of the fifth embodiment; FIG. 10 is a flowchart showing a sixth embodiment of a control process for a VVT mechanism; FIG. 11 is a time chart for explaining the operation and function of the sixth embodiment.

[0009] An embodiment of the present invention will be described below. Fig. 1 is a system diagram of an internal combustion engine for a vehicle equipped with an electric variable valve timing mechanism as one form of actuator using a motor. An internal combustion engine 101 is equipped with an intake air mass sensor 103 in an intake duct 102 that detects an intake air flow rate QA of the internal combustion engine 101. The intake duct 102 branches into intake ports 102a that introduce air and fuel into combustion chambers 104 of each cylinder, and the intake ports 102a are opened and closed by intake valves 105.

[0010] Fuel injection valves 106 inject fuel into intake ports 102a of each cylinder. The fuel drawn into combustion chamber 104 together with air is ignited and burned by spark from spark plugs 107. The combustion pressure then pushes piston 108 down toward crankshaft 109, driving it to rotate.

[0011] The ignition module 116 includes an ignition coil and a power transistor that controls the supply of electricity to the ignition coil, and supplies ignition energy to the spark plug 107. In addition, the exhaust valve 110 opens and closes the exhaust port 102b that leads exhaust gas out of the combustion chamber 104. A catalytic converter 112 that contains a catalyst such as a three-way catalyst is disposed in an exhaust pipe 111 where the exhaust ports 102b of each cylinder are gathered.

[0012] The intake valve 105 opens and closes according to the rotational position of an intake camshaft 115a, which is rotationally driven by the crankshaft 109. The exhaust valve 110 opens and closes according to the rotational position of an exhaust camshaft 115b, which is rotationally driven by the crankshaft 109.

[0013] Here, the internal combustion engine 101 is equipped with an electric variable valve timing mechanism 114 (hereinafter referred to as the VVT ​​mechanism 114) that continuously varies the valve timing of the intake valve 105, which is an engine valve. The VVT ​​mechanism 114 is a variable valve timing mechanism that changes the rotational phase of the intake camshaft 115a relative to the crankshaft 109 based on the difference in rotational speed between the output shaft of the brushless motor 12 and a drive rotor that rotates in synchronization with the crankshaft 109. The above-mentioned type of variable valve timing mechanism is a well-known mechanism disclosed, for example, in Japanese Patent Application Laid-Open No. 2018-123716. The VVT ​​mechanism 114 corresponds to one aspect of an actuator that uses a motor.

[0014] The structure of VVT mechanism 114 will be outlined below. In one aspect, VVT mechanism 114 includes a drive rotor that rotates in synchronization with crankshaft 109, a driven rotor that rotates integrally with intake camshaft 115a, and a torque transmission unit that transmits torque output from brushless motor 12 to the driven rotor. The torque transmission unit includes cylindrical planetary gears that are disposed inside the drive rotor and driven rotor, and cylindrical planet carriers that are disposed inside the planetary gears, and is configured so that the planetary gears can perform planetary motion by making the rotational speed of the planet carrier different from the rotational speed of the drive rotor.

[0015] When the planetary carrier is rotated at the same speed as the drive rotor by the drive of brushless motor 12, the rotational phase of the driven rotor relative to the drive rotor, i.e., the rotational phase of intake camshaft 115a relative to crankshaft 109, is maintained. On the other hand, when the planetary carrier is rotated at a slower speed than the drive rotor by the drive of brushless motor 12, the rotational phase changes in the direction that retards the valve timing.

[0016] Furthermore, when the planetary carrier rotates faster than the drive rotor due to drive of brushless motor 12, the rotational phase changes in the direction in which the valve timing advances. In this way, VVT mechanism 114 changes the rotational phase of the driven rotor relative to the drive rotor based on the difference in rotational speed between the drive rotor and brushless motor 12, thereby changing the rotational phase of intake camshaft 115a relative to crankshaft 109.

[0017] The control system that controls the operation of the internal combustion engine 101 includes an engine control module 210 (hereinafter referred to as ECM 210) that controls fuel injection by the fuel injection valves 106 and ignition by the spark plugs 107, and a VVT controller 220 that controls the brushless motor 12 of the VVT ​​mechanism 114 in response to control commands from the ECM 210. As described above, the VVT ​​mechanism 114 is controlled by a control device 230 that combines the ECM 210 and the VVT ​​controller 220. The ECM 210 and the VVT ​​controller 220 are connected to a bus of an in-vehicle network such as a Controller Area Network (CAN), and communication between the ECM 210 and the VVT ​​controller 220 is performed via the in-vehicle network.

[0018] Here, ECM 210 outputs a control command to VVT controller 220, and therefore corresponds to the higher-level control device of the two control devices 210, 220 that constitute control device 230. Furthermore, VVT controller 220 controls brushless motor 12 based on a control command from ECM 210, and therefore corresponds to the lower-level control device of the two control devices 210, 220 that constitute control device 230.

[0019] The ECM 210 includes a microcomputer 210a, and the VVT ​​controller 220 includes a microcomputer 220a. Each of the microcomputers 210a and 220a includes a processor, a non-volatile memory, a volatile memory, and the like.

[0020] The ECM 210 acquires signals output by various sensors and performs arithmetic processing in accordance with programs stored in nonvolatile memory to calculate and output manipulated variables for the fuel injection valves 106, ignition module 116, etc. Furthermore, the ECM 210 calculates a target value for feedback control of the VVT ​​mechanism 114 and outputs a signal of the calculated target value as a control command signal to the VVT ​​controller 220. The VVT ​​controller 220 then acquires the control command signal sent by the ECM 210 and signals output by the various sensors and performs arithmetic processing in accordance with programs stored in nonvolatile memory to calculate and output the manipulated variable for the VVT ​​mechanism 114, specifically, the motor manipulated variable for the brushless motor 12.

[0021] As the various sensors described above, the internal combustion engine 101 is equipped with an intake air mass sensor 103 that detects an intake air flow rate QA of the internal combustion engine 101, a crank angle sensor 203 that outputs a crank angle signal POS for each predetermined angular position of the crankshaft 109, an accelerator opening sensor 206 that detects the depression amount of an accelerator pedal 207, in other words, the accelerator opening ACC, a cam angle sensor 204 that outputs a cam angle signal CAM for each predetermined angular position of the intake camshaft 115a, a water temperature sensor 208 that detects the temperature TW of the cooling water of the internal combustion engine 101, and an air-fuel ratio sensor 209 that is installed in the exhaust pipe 111 upstream of the catalytic converter 112 and detects the air-fuel ratio AF based on the oxygen concentration in the exhaust.

[0022] The crank angle signal POS output by the crank angle sensor 203 is a pulse signal for each unit crank angle, and its signal output pattern is set so that one or a series of multiple pulses are missing for each crank angle corresponding to the stroke phase difference between the cylinders. Here, the position of the missing pulse signal in the crank angle signal POS is detected as a reference crank angle position.

[0023] The cam angle signal CAM output by the cam angle sensor 204 is output for each crank angle corresponding to the stroke phase difference between the cylinders. That is, if the internal combustion engine 101 is a four-cylinder engine, the cam angle sensor 204 outputs the cam angle signal CAM for each 180 degrees of crank angle. The ECM 210 acquires the signals output by these various sensors and also acquires an on / off signal from an ignition switch 205, which is the main switch for operating and stopping the internal combustion engine 101.

[0024] Furthermore, brushless motor 12 of VVT mechanism 114 is, for example, a three-phase brushless motor and includes Hall sensors 12u, 12v, and 12w as motor rotational position sensors that detect the positional relationship between the rotor and three-phase coils, i.e., a U-phase coil, a V-phase coil, and a W-phase coil. VVT controller 220 acquires motor rotational position signals output by Hall sensors 12u, 12v, and 12w.

[0025] The ECM 210 calculates a target rotational phase, which is a target value of the rotational phase (VVT conversion angle) of the intake camshaft 115a relative to the crankshaft 109, based on engine operating conditions such as the engine load and engine speed obtained from output signals from the various sensors described above. The ECM 210 also obtains an actual rotational phase (control amount) based on the crank angle signal POS and the cam angle signal CAM.

[0026] The target rotational phase is expressed, for example, as an advance angle [deg] from the most retarded position within the variable range of the rotational phase by VVT mechanism 114. ECM 210 then obtains a target motor rotational speed for brushless motor 12 by comparing the actual rotational phase with the target rotational phase, and transmits a signal of the target motor rotational speed to VVT controller 220 as a control command signal.

[0027] VVT controller 220 obtains a target motor current by acquiring a target motor rotation speed signal from ECM 210 and comparing the target motor rotation speed with the actual motor rotation speed. Furthermore, VVT controller 220 obtains an operation amount of brushless motor 12 by comparing the target motor current with the actual motor current, and controls the supply of current to brushless motor 12 based on the obtained operation amount.

[0028] 2 is a block diagram showing the control function of the brushless motor 12 by a control device 230 including an ECM 210 and a VVT controller 220. The ECM 210 has a target rotational phase calculation unit 211 and a rotational phase feedback control unit 212. The target rotational phase calculation unit 211 calculates a target rotational phase of the VVT ​​mechanism 114 based on the operating conditions of the internal combustion engine 101, such as the engine load and engine speed.

[0029] Rotation phase feedback control unit 212 acquires a signal of the target rotation phase calculated by target rotation phase calculation unit 211 and a signal of the actual rotation phase. Rotation phase feedback control unit 212 then performs an operation to correct the target motor rotation speed so that the actual rotation phase approaches the target rotation phase, and transmits a signal of the target motor rotation speed to VVT controller 220.

[0030] The ECM 210 (rotation phase feedback control unit 212) transmits a signal of the target motor rotation speed to the VVT ​​controller 220 via an in-vehicle network. As the correction action, a proportional action (P action), an integral action (I action), a differential action (D action), etc. are used.

[0031] On the other hand, VVT controller 220 has a motor rotational speed feedback control unit 221 and a motor current feedback control unit 222. Motor rotational speed feedback control unit 221 receives a target motor rotational speed signal from ECM 210 (rotation phase feedback control unit 212), and also receives an actual motor rotational speed signal calculated from the outputs of Hall sensors 12u, 12v, and 12w. Motor rotational speed feedback control unit 221 then corrects the target motor current so that the actual motor rotational speed approaches the target motor rotational speed, and outputs a target motor current signal.

[0032] Motor current feedback control unit 222 receives a target motor current signal and an actual motor current signal from motor rotational speed feedback control unit 221. Motor current feedback control unit 222 then corrects the manipulated variable of brushless motor 12 so that the actual motor current approaches the target motor current, and outputs a manipulated variable signal. VVT controller 220 then controls the supply of current to brushless motor 12 in accordance with the manipulated variable output from motor current feedback control unit 222.

[0033] The combination (first combination) of the above-described target rotational phase calculation unit 211, rotational phase feedback control unit 212, motor rotational speed feedback control unit 221, and motor current feedback control unit 222 constitutes a control system for feedback controlling the VVT ​​mechanism 114 while the internal combustion engine 101 is operating, in other words, in the rotational state of the drive rotor that rotates in synchronous with the crankshaft 109 in the VVT ​​mechanism 114. In other words, when the internal combustion engine 101 is operating, the ECM 210 and the VVT ​​controller 220 use the three feedback control units, namely the rotational phase feedback control unit 212, the motor rotational speed feedback control unit 221, and the motor current feedback control unit 222, in other words, three feedback control loops, to control the VVT ​​mechanism 114 (brushless motor 12).

[0034] On the other hand, the control device 230, which is composed of the ECM 210 and the VVT ​​controller 220, feedback controls the VVT ​​mechanism 114 using a different combination when the internal combustion engine 101 is stopped, in other words, when the drive rotor that rotates in synchronization with the crankshaft 109 in the VVT ​​mechanism 114 is stopped. In other words, when the internal combustion engine 101 is stopped, the control device 230 controls the rotational phase to a target rotational phase for restart in preparation for restarting the internal combustion engine 101, and at this time controls the VVT ​​mechanism 114 (brushless motor 12) using a feedback control structure that is different from that when the internal combustion engine 101 is operating.

[0035] The ECM 210 has a target relative angle calculation unit 213 as a functional unit for controlling the VVT ​​mechanism 114 when the internal combustion engine 101 is stopped. The target relative angle calculation unit 213 calculates the difference between the actual rotational phase at the timing when the internal combustion engine 101 is stopped and the target rotational phase when the internal combustion engine 101 is stopped as a target relative angle (in other words, a target operation amount or a target rotational phase change amount). In other words, the target relative angle is the value of the target rotational phase when the internal combustion engine 101 is stopped, when the actual rotational phase at the timing when the internal combustion engine 101 is stopped is set as a zero point. The target rotational phase when the internal combustion engine 101 is stopped is stored in a non-volatile memory of the ECM 210 as an appropriate rotational phase when the internal combustion engine 101 is restarted.

[0036] Furthermore, VVT controller 220 has a motor relative angle feedback control unit 223 and a target motor current switching unit 224 as functional units for controlling VVT mechanism 114 when internal combustion engine 101 is stopped. Motor relative angle feedback control unit 223 acquires a signal of the target relative angle from target relative angle calculation unit 213 of ECM 210 via the in-vehicle network, and also acquires a signal of the actual relative angle.

[0037] When the internal combustion engine 101 is stopped, the rotation of the drive rotor is also stopped, and therefore the rotational phase of the intake camshaft 115a relative to the crankshaft 109 changes depending on the rotational direction and rotational angle of the brushless motor 12. Therefore, the actual relative angle, in other words, the amount of change in the rotational phase after the internal combustion engine 101 has stopped, can be determined from the rotational direction and rotational angle of the brushless motor 12.

[0038] Then, motor relative angle feedback control unit 223 performs a target motor current correction operation so that the actual relative angle approaches the target relative angle, in other words, so that the amount of change in rotational phase from the rotational phase when internal combustion engine 101 is stopped approaches the target value, and outputs a target motor current signal. Target motor current switching unit 224 is a functional unit that acquires the target motor current signal output by motor rotational speed feedback control unit 221 and the target motor current signal output by motor relative angle feedback control unit 223, and selects and outputs one of these two target motor currents.

[0039] Here, the target motor current switching unit 224 switches the target motor current based on an engine stop signal (engine stall signal) that is a signal that indicates whether the internal combustion engine 101 is in an operating state or a stopped state. In detail, when the internal combustion engine 101 is in an operating state, the target motor current switching unit 224 outputs the target motor current calculated by the motor rotational speed feedback control unit 221 to the motor current feedback control unit 222. On the other hand, when the internal combustion engine 101 is in a stopped state, the target current switching unit 224 outputs the target motor current calculated by the motor relative angle feedback control unit 223 to the motor current feedback control unit 222.

[0040] In this way, in the control of the VVT ​​mechanism 114 by the control device 230 constituted by the ECM 210 and the VVT ​​controller 220, when the internal combustion engine 101 is operating, the control device 230 feedback-controls the rotational phase of the VVT ​​mechanism 114 to a target value during operation using three feedback control loops (first combination) consisting of the rotational phase feedback control unit 212, the motor rotational speed feedback control unit 221, and the motor current feedback control unit 222. On the other hand, when the internal combustion engine 101 is stopped, the control device 230 feedback-controls the rotational phase of the VVT ​​mechanism 114 to a target value during stoppage (in other words, a target value for restart) using two feedback control loops (second combination) consisting of the motor relative angle feedback control unit 223 and the motor current feedback control unit 222.

[0041] In other words, the number of feedback control loops used to control the VVT ​​mechanism 114 is three when the internal combustion engine 101 is operating, but is reduced to two when the internal combustion engine 101 is stopped. In other words, in the control of the VVT ​​mechanism 114 by the control device 230, the number of feedback control loops used for control is reduced when the drive rotor that rotates synchronously with the crankshaft 109 in the VVT ​​mechanism 114 is stopped compared to when it is rotating.

[0042] When internal combustion engine 101 is stopped, the rotational speed of the drive rotor that rotates synchronously with crankshaft 109 becomes zero, making control based on the rotational speed difference unnecessary. For this reason, motor rotational speed feedback control unit 221 and rotation phase feedback control unit 212 that sets the target motor rotational speed to be given to motor rotational speed feedback control unit 221 are excluded from the feedback control configuration. Meanwhile, motor relative angle feedback control unit 223 that performs an operation to correct the target motor current so that the actual relative angle approaches the target relative angle is added to the feedback control configuration in place of motor rotational speed feedback control unit 221 and rotation phase feedback control unit 212.

[0043] Furthermore, when the internal combustion engine 101 is operating, feedback control is performed in the VVT ​​controller 220 using a signal of the target motor rotation speed calculated by a rotation phase feedback control unit 212 provided in the ECM 210. In contrast, when the internal combustion engine 101 is stopped, the signal of the target motor rotation speed calculated by the rotation phase feedback control unit 212 provided in the ECM 210 is not used for feedback control in the VVT ​​controller 220, and the VVT ​​mechanism 114 is feedback controlled only by the correction operation performed within the VVT ​​controller 220.

[0044] 3 shows a control process of the first embodiment in which the control device 230 switches the configuration and number of feedback control loops depending on whether the internal combustion engine 101 is operating or stopped, in other words, whether the drive rotor of the VVT ​​mechanism 114 is rotating or stopped, in control of the VVT ​​mechanism 114. In step S401, the control device 230 determines whether the internal combustion engine 101 is operating or stopped based on the on / off signal of the ignition switch 205, the crank angle signal POS, the cam angle signal CAM, etc.

[0045] If the control device 230 determines in step S401 that the internal combustion engine 101 is in an operating state (a state in which the drive rotor is rotating), the process proceeds to step S402 (rotation phase feedback control unit 212). Then, in step S402, the control device 230 performs an operation to correct the target motor rotation speed of the brushless motor 12 so that the actual rotation phase approaches the target rotation phase.

[0046] On the other hand, if the control device 230 determines that the internal combustion engine 101 is in a stopped state (a stopped state of the drive rotor), the process proceeds to step S403 (target relative angle calculation unit 213). Then, in step S403, the control device 230 performs a process of calculating a target relative angle (in other words, a target rotational phase change amount) that is the difference between the actual rotational phase at the timing when the internal combustion engine 101 is stopped and the target rotational phase when the internal combustion engine 101 is in a stopped state. Also, in step S403, the control device 230 sets a request for switching to feedback control when the internal combustion engine 101 is in a stopped state (hereinafter referred to as a request for switching to control for a stopped state).

[0047] After the process of step S402 or step S403, the control device 230 proceeds to step S404 (target motor current switching unit 224) and determines whether a request for switching to stop state control has been set. Here, if a request for switching to stop state control has not been set, in other words, if the internal combustion engine 101 is in an operating state, the control device 230 proceeds to step S405 (motor rotational speed feedback control unit 221). On the other hand, if a request for switching to stop state control has been set, in other words, if the internal combustion engine 101 is in a stop state, the control device 230 proceeds to step S406 (motor relative angle feedback control unit 223).

[0048] In step S405, the control device 230 corrects the target motor current so that the actual motor rotation speed approaches the target motor rotation speed calculated in step S402. Meanwhile, in step S406, the control device 230 corrects the target motor current so that the actual relative angle approaches the target relative angle, in other words, so that the amount of change in the actual rotation phase approaches the target value.

[0049] After setting the target motor current in step S405 or step S406, control device 230 proceeds to step S407 (motor current feedback control unit 222). In step S407, control device 230 performs an operation to correct the manipulated variable of brushless motor 12 so that the actual motor current approaches the target motor current set in step S405 or step S406, and outputs a manipulated variable signal to the drive circuit of brushless motor 12.

[0050] As described above, when the internal combustion engine 101 is in an operating state (in other words, when the drive rotor is rotating), the control device 230 controls the drive of the brushless motor 12 by proceeding in the order of step S401, step S402 (rotation phase feedback control unit 212), step S404 (target motor current switching unit 224), step S405 (motor rotational speed feedback control unit 221), and step S407 (motor current feedback control unit 222). On the other hand, when the internal combustion engine 101 is in a stopped state (in other words, when the drive rotor is stopped), the control device 230 controls the drive of the brushless motor 12 by proceeding in the order of step S401, step S403 (target relative angle calculation unit 213), step S404 (target motor current switching unit 224), step S406 (motor relative angle feedback control unit 223), and step S407 (motor current feedback control unit 222).

[0051] 4 illustrates changes in the rotation speed of the internal combustion engine 101, the rotation phase of the VVT ​​mechanism 114, a request for switching to control for a stopped state, and the operation / stop determination of the internal combustion engine 101 when the internal combustion engine 101 stops from an operating state. When the rotation speed of the internal combustion engine 101 decreases and the rotation of the internal combustion engine 101 stops at time t1, it is determined that the internal combustion engine 101 has stopped, and based on this determination, the target rotation phase is switched from a target value when the internal combustion engine 101 is in an operating state to a target value when the internal combustion engine 101 is in a stopped state.

[0052] Furthermore, when it is determined at time t1 that internal combustion engine 101 has stopped, a request for switching to control for a stopped state is set. Then, in response to the determination that internal combustion engine 101 has stopped, target relative angle calculation unit 213 calculates, as a target relative angle, the difference between the actual rotational phase at the timing when internal combustion engine 101 has stopped and the target rotational phase in the stopped state of internal combustion engine 101. Then, motor relative angle feedback control unit 223 performs an operation to correct the target current of brushless motor 12 so that the actual relative angle approaches the target relative angle, in other words, so that the actual rotational phase when internal combustion engine 101 has stopped changes to the target rotational phase in the stopped state of internal combustion engine 101.

[0053] As described above, the control device 230 that performs feedback control of the VVT ​​mechanism 114 switches the number and configuration of feedback control loops used for feedback control of the rotational phase depending on whether the internal combustion engine 101 is operating or stopped. This ensures responsiveness and convergence to the target rotational phase in both the operating and stopped states of the internal combustion engine 101.

[0054] The reason why the control device 230 achieves the above-described effects will be explained below. First, it is assumed that the control device 230 performs feedback control of the brushless motor 12 using a combination (first combination) of the rotational phase feedback control unit 212, the motor rotational speed feedback control unit 221, and the motor current feedback control unit 222, i.e., three feedback control loops, even when the internal combustion engine 101 is stopped, just as when the internal combustion engine 101 is operating. In this case, if the load on the brushless motor 12 increases when the rotational phase is changed due to the internal combustion engine 101 being stopped, a control delay caused by using the three feedback control loops becomes apparent, and there is a possibility that convergence to the target rotational phase (target rotational phase for restart) when the internal combustion engine 101 is stopped will be delayed.

[0055] The time chart in Figure 5 illustrates an example of a change in the actual rotational phase toward the target rotational phase for the stopped state when brushless motor 12 is controlled by a combination of rotational phase feedback control unit 212, motor rotational speed feedback control unit 221, and motor current feedback control unit 222, even when internal combustion engine 101 is stopped, just as when it is running. Figure 5 also shows how, when internal combustion engine 101 switches from the operating state to the stopped state, a feedback control delay becomes apparent as the load on brushless motor 12 increases, causing the actual rotational phase to overshoot the target rotational phase for the stopped state and then converge with a delay.

[0056] In response to this, when the internal combustion engine 101 changes from an operating state to a stopped state, the control device 230 switches the number and configuration of feedback control loops so as to control the rotation phase by a combination of the motor relative angle feedback control unit 223 and the motor current feedback control unit 222. With this configuration, the number of feedback control loops is reduced, thereby suppressing feedback control delay and making it possible to reduce convergence delay.

[0057] Furthermore, in addition to the reduction in the number of feedback control loops, the configuration in which motor relative angle feedback control unit 223 and motor current feedback control unit 222 are provided in VVT controller 220, and the output (target value) of the feedback control unit of ECM 210 is not used by the feedback control unit of VVT controller 220, also contributes to suppressing feedback control delays. In other words, if the output of the feedback control unit in ECM 210 is used by the feedback control unit of VVT controller 220, the output (target value) of the feedback control unit is passed through communication between ECM 210 and VVT controller 220, and the time required for corrective action calculation in ECM 210 and the communication time between ECM 210 and VVT controller 220 become factors in feedback control delays. In contrast, if feedback control is performed only by the feedback control unit provided in VVT controller 220, the output of the feedback control unit is not passed through communication between the controllers, and therefore feedback control delays as a whole can be suppressed.

[0058] The time chart of Fig. 6 illustrates an example of a change in the actual rotational phase toward a target rotational phase in a stopped state when the internal combustion engine 101 is in a stopped state and the rotational phase is feedback-controlled by a combination of the motor relative angle feedback control unit 223 and the motor current feedback control unit 222. Fig. 6 also shows that controlling the rotational phase by a combination of the motor relative angle feedback control unit 223 and the motor current feedback control unit 222 in a stopped state of the internal combustion engine 101 improves the responsiveness and convergence of the actual rotational phase toward the target rotational phase in the stopped state.

[0059] The method of estimating the change in the load on brushless motor 12 is not limited to a method based on the operation / stop determination of internal combustion engine 101. For example, control device 230 can switch the feedback control when a state in which the responsiveness or convergence to the target rotation phase is worse than a predetermined level, in other words, a state in which the tracking delay of the controlled variable with respect to the target value is greater than a predetermined level, is attributed to an increase in the load on brushless motor 12.

[0060] 7 shows a control process of the second embodiment in which the control device 230 determines a load change on the brushless motor 12 based on the delay in the controlled variable following the target value and switches the feedback control. That is, in the second embodiment, the target motor current switching unit 224 selects and outputs either the target motor current signal output by the motor rotational speed feedback control unit 221 or the target motor current signal output by the motor relative angle feedback control unit 223 based on the magnitude of the delay in the controlled variable following the target value.

[0061] In step S501, the control device 230 (target motor current switching unit 224 of the VVT ​​controller 220) determines whether both a first condition, that is, the absolute value of the deviation between the actual rotational phase and the target rotational phase is greater than a first threshold value (first threshold value > 0), and a second condition, that is, the amount of change in the actual rotational phase per predetermined time (in other words, the rate of change of the actual rotational phase) is equal to or less than a second threshold value, are satisfied, or whether at least one of the first condition and the second condition is not satisfied.

[0062] The first threshold is a threshold for determining whether the deviation between the actual rotation phase and the target rotation phase is greater than a tolerance and whether the actual rotation phase needs to be brought closer to the target rotation phase, and the second threshold is a threshold for determining whether the actual response speed is slower than the slowest response speed allowed when bringing the actual rotation phase closer to the target rotation phase.

[0063] In other words, a state in which both the first condition and the second condition are satisfied is a state in which the deviation between the actual rotational phase and the target rotational phase is greater than the allowable value, and although it is necessary to bring the actual rotational phase closer to the target rotational phase, the speed at which the actual rotational phase approaches the target rotational phase is too slow (including a state in which the actual rotational phase does not change). For example, when the load on brushless motor 12 increases as internal combustion engine 101 stops, both the first condition and the second condition are satisfied at time t21 in FIG.

[0064] If at least one of the first condition and the second condition is not met, control device 230 estimates that the load on brushless motor 12 is small enough that switching of feedback control is not necessary, and proceeds to step S502. Then, in step S502, control device 230 performs an operation to correct the target motor rotation speed of brushless motor 12 so that the actual rotation phase approaches the target rotation phase. In other words, if at least one of the first condition and the second condition is not met, control device 230 controls brushless motor 12 using a combination of rotation phase feedback control unit 212, motor rotation speed feedback control unit 221, and motor current feedback control unit 222.

[0065] On the other hand, if both the first condition and the second condition are met, the control device 230 estimates that the load on the brushless motor 12 has become large enough to require switching of the feedback control, and proceeds to step S503 (target relative angle calculation unit 213). Then, in step S503, the control device 230 performs processing to obtain the target relative angle and processing to set a request for switching of the feedback control. In other words, if both the first condition and the second condition are met, the control device 230 estimates that the load on the brushless motor 12 has become large enough to require switching of the feedback control, and controls the brushless motor 12 by a combination of the motor relative angle feedback control unit 223 and the motor current feedback control unit 222.

[0066] After processing in step S502 or step S503, the control device 230 proceeds to step S504 to determine whether a feedback control switching request has been set. If a switching request has been set, the control device 230 proceeds to step S506; if a switching request has not been set, the control device 230 proceeds to step S505. Then, in step S507, the control device 230 performs an operation to correct the manipulated variable based on the target motor current set in step S505 or step S506. Note that the processing in steps S504 to S507 is similar to the processing in steps S404 to S407 in the flowchart of FIG. 3, and therefore detailed description thereof will be omitted.

[0067] According to the second embodiment, the tracking ability of the rotational phase when the load on the brushless motor 12 increases (including when the internal combustion engine 101 is stopped) is improved, and convergence to the target rotational phase is accelerated when the load is high. When determining the load on the brushless motor 12 based on the tracking delay of the controlled variable with respect to the target value, the control device 230 can determine that the load on the brushless motor 12 is increasing when the first and second conditions are satisfied, or when the state in which the first condition is satisfied continues for more than a predetermined time.

[0068] Incidentally, the lower the temperature of internal combustion engine 101, the greater the frictional resistance, and the greater the load on brushless motor 12 when the rotational phase is changed by VVT mechanism 114. Therefore, when determining the load on brushless motor 12, control device 230 can set a request to switch to feedback control by adding a determination of the temperature condition of internal combustion engine 101, in other words, the temperature condition of VVT mechanism 114.

[0069] The flowchart in Fig. 8 shows a control process of the third embodiment in which feedback control is switched by determining the temperature condition of the internal combustion engine 101 in addition to determining whether the internal combustion engine 101 is operating or stopped. In the flowchart in Fig. 8, steps S602 to S607 perform the same processing as steps S402 to S407 in Fig. 3, and only the processing in step S601 differs from step S401 in Fig. 3. Therefore, detailed description of steps S602 to S607 will be omitted, and the processing content in step S601 will be described.

[0070] In step S601, the control device 230 (target motor current switching unit 224 of the VVT ​​controller 220) determines whether the internal combustion engine 101 has stopped based on the on / off signal of the ignition switch 205, and also determines whether the temperature of the internal combustion engine 101 at that time is equal to or lower than a set temperature, that is, a predetermined cold-engine state. The temperature of the internal combustion engine 101 is represented by the temperature of the lubricating oil of the internal combustion engine 101 detected by an oil temperature sensor, the temperature of the cooling water of the internal combustion engine 101 detected by a water temperature sensor, or the like.

[0071] Here, if the internal combustion engine 101 is in operation and / or the temperature of the internal combustion engine 101 exceeds the set temperature, the control device 230 determines that the load on the brushless motor 12 is relatively small and therefore the tracking delay of the rotational phase can be kept relatively small without switching the feedback control, and proceeds to step S602. In step S602 (rotational phase feedback control unit 212), the control device 230 performs an operation to correct the target motor rotational speed of the brushless motor 12 so that the actual rotational phase approaches the target rotational phase. In other words, if the internal combustion engine 101 is in operation and / or the temperature of the internal combustion engine 101 exceeds the set temperature, the control device 230 controls the brushless motor 12 by a combination of the rotational phase feedback control unit 212, the motor rotational speed feedback control unit 221, and the motor current feedback control unit 222.

[0072] On the other hand, when the internal combustion engine 101 is in a stopped state and the temperature of the internal combustion engine 101 is equal to or lower than the set temperature, the control device 230 determines that the load on the brushless motor 12 is greater than the threshold value and that the condition for the rotational phase tracking delay to exceed the allowable level is satisfied, and proceeds to step S603 (target relative angle calculation unit 213). Then, in step S603, the control device 230 performs processing to determine the target relative angle and processing to set a request for switching to control for the stopped state, thereby suppressing the rotational phase tracking delay.

[0073] In other words, when the internal combustion engine 101 is stopped and the temperature of the internal combustion engine 101 is equal to or lower than a set temperature, the control device 230 controls the brushless motor 12 by combining the motor relative angle feedback control unit 223 and the motor current feedback control unit 222. In this way, if the configuration is such that the feedback control of the rotational phase is switched on and on the condition that the internal combustion engine 101 is stopped and the temperature of the internal combustion engine 101 is equal to or lower than a set temperature, it is possible to suppress the tracking delay by switching the feedback control (reducing the number of feedback control loops) when the internal combustion engine 101 is stopped and the tracking delay of the rotational phase is particularly large.

[0074] The flowchart in Fig. 9 shows a control process of the fourth embodiment in which feedback control is switched by determining the follow-up delay state of the rotation phase and determining the temperature condition of the internal combustion engine 101. In the flowchart in Fig. 9, steps S702 to S707 perform the same processing as steps S502 to S507 in Fig. 7, and only the processing in step S701 differs from step S501 in Fig. 7. Therefore, detailed description of steps S702 to S707 will be omitted, and the processing content in step S701 will be described.

[0075] In step S701, the control device 230 (target motor current switching unit 224 of the VVT ​​controller 220) determines whether all of the following conditions are met: a first condition that the absolute value of the deviation between the actual rotational phase and the target rotational phase is greater than a first threshold value; a second condition that the amount of change in the actual rotational phase per specified time is equal to or less than a second threshold value; and a third condition that the temperature of the internal combustion engine 101 is equal to or less than a set temperature, that is, the internal combustion engine 101 is in a specified cold state.

[0076] If at least one of the first, second, and third conditions is not satisfied, the control device 230 determines that the load on the brushless motor 12 is relatively small and therefore the tracking delay of the rotational phase can be kept relatively small without switching the feedback control, and proceeds to step S702. In step S702 (rotational phase feedback control unit 212), the control device 230 performs an operation to correct the target motor rotational speed of the brushless motor 12 so that the actual rotational phase approaches the target rotational phase. In other words, if no tracking delay of the rotational phase is recognized and the temperature of the internal combustion engine 101 is higher than the set temperature, the control device 230 controls the brushless motor 12 by a combination of the rotational phase feedback control unit 212, the motor rotational speed feedback control unit 221, and the motor current feedback control unit 222.

[0077] On the other hand, if all of the first, second, and third conditions are satisfied, the control device 230 recognizes a tracking delay in the rotational phase and determines that the temperature conditions are such that the tracking delay will be exacerbated, and proceeds to step S703 (target relative angle calculation unit 213). Then, in step S703, the control device 230 performs a process of calculating the target relative angle and a process of setting a request for switching to stop state control, thereby suppressing the tracking delay in the rotational phase.

[0078] That is, when a tracking delay in the rotational phase is recognized and the temperature conditions are such that the tracking delay increases, control device 230 controls brushless motor 12 by combining motor relative angle feedback control unit 223 and motor current feedback control unit 222. With this configuration, when a tracking delay in the rotational phase is recognized and the temperature conditions are such that the tracking delay increases, the tracking delay can be suppressed by switching feedback control (reducing the number of feedback control loops).

[0079] Incidentally, deterioration in controllability of the rotational phase, such as a delay in tracking of the actual rotational phase relative to the target rotational phase, can also occur due to an increase in the processing load of the control device 230. Here, the processing load of the control device 230 refers to a calculation load, a communication load, etc., and in the case of the control device 230 configured by combining the ECM 210 and the VVT ​​controller 220, the controllability of the rotational phase may deteriorate if the calculation load of the ECM 210 increases or if the communication load (in other words, the line load or the amount of communication) between the ECM 210 and the VVT ​​controller 220 increases. In response to such an increase in the processing load of the control device 230, feedback control can be switched (the number of feedback control loops is reduced) to reduce the calculation load of the ECM 210 and the communication load between the ECM 210 and the VVT ​​controller 220, thereby preventing deterioration in controllability of the rotational phase.

[0080] The flowchart in Fig. 10 shows a control process of the fifth embodiment in which feedback control is switched depending on the calculation load of the ECM 210. In the flowchart in Fig. 10, steps S802 to S807 perform the same processing as steps S502 to S507 in Fig. 7, and only the processing in step S801 differs from step S501 in Fig. 7. Therefore, detailed description of steps S802 to S807 will be omitted, and the processing content in step S801 will be described.

[0081] In step S801, the control device 230 (target motor current switching unit 224 of the VVT ​​controller 220) determines whether the calculation load of the ECM 210 is higher than a threshold (set value). The threshold for the calculation load of the ECM 210 is a threshold for determining whether the calculation load is large enough to deteriorate the controllability of the rotation phase. In other words, the threshold for the calculation load of the ECM 210 is adapted so that if the calculation load of the ECM 210 is equal to or less than the threshold, it can be determined that necessary and sufficient controllability is ensured, and if the calculation load of the ECM 210 exceeds the threshold, it can be determined that there is a risk of deterioration in controllability.

[0082] If the calculation load in ECM 210 is equal to or less than the threshold, control device 230 proceeds to step S802 (rotational phase feedback control unit 212) and performs an operation to correct the target motor rotational speed of brushless motor 12 so that the actual rotational phase approaches the target rotational phase. In other words, if the calculation load in ECM 210 is equal to or less than the threshold, control device 230 controls brushless motor 12 by a combination of rotational phase feedback control unit 212 provided in ECM 210 and motor rotational speed feedback control unit 221 and motor current feedback control unit 222 provided in VVT controller 220.

[0083] On the other hand, when the calculation load on ECM 210 is higher than the threshold, control device 230 proceeds to step S803 (target relative angle calculation unit 213) and performs processing to determine the target relative angle and processing to set a request for switching to stop state control, thereby suppressing a tracking delay of the rotational phase. In other words, when the calculation load on ECM 210 is higher than the threshold, control device 230 controls brushless motor 12 by a combination of motor relative angle feedback control unit 223 and motor current feedback control unit 222 provided in VVT controller 220, without using rotational phase feedback control unit 212 provided in ECM 210. With this configuration, when the calculation load on ECM 210 becomes higher than the threshold, control device 230 switches to control of the rotational phase without using rotational phase feedback control unit 212 provided in ECM 210, thereby suppressing a deterioration in controllability of VVT mechanism 114.

[0084] 11 illustrates the correlation between changes in the computational load of the ECM 210 and a request to switch the feedback control of the VVT ​​mechanism 114. At time t51 in FIG. 11, when the computational load of the ECM 210 exceeds a threshold value, a request to switch the feedback control is generated.

[0085] Then, when a request to switch feedback control occurs, feedback control is switched from a combination of rotation phase feedback control unit 212 provided in ECM 210 and motor rotational speed feedback control unit 221 and motor current feedback control unit 222 provided in VVT controller 220 to feedback control using a combination of motor relative angle feedback control unit 223 and motor current feedback control unit 222 provided in VVT controller 220. In other words, when the calculation load of ECM 210 becomes higher than a threshold, control device 230 reduces the number of feedback control loops used to control brushless motor 12, and performs feedback control of brushless motor 12 using motor relative angle feedback control unit 223 and motor current feedback control unit 222 provided in VVT controller 220, without using rotation phase feedback control unit 212 provided in ECM 210.

[0086] 11, when the calculation load of ECM 210 falls below the threshold, the request to switch feedback control is canceled. As a result, feedback control returns from the combination of motor relative angle feedback control unit 223 and motor current feedback control unit 222 provided in VVT controller 220 to feedback control using a combination of rotation phase feedback control unit 212 provided in ECM 210 and motor rotational speed feedback control unit 221 and motor current feedback control unit 222 provided in VVT controller 220.

[0087] The flowchart in Fig. 12 shows a control process of the sixth embodiment in which feedback control is switched depending on the communication load between the ECM 210 and the VVT ​​controller 220. In the flowchart in Fig. 12, steps S902 to S907 perform the same processing as steps S502 to S507 in Fig. 7, and only the processing in step S901 differs from step S501 in Fig. 7. Therefore, detailed description of steps S902 to S907 will be omitted, and the processing content in step S901 will be described.

[0088] In step S901, control device 230 (target motor current switching unit 224 of VVT controller 220) determines whether the communication load between ECM 210 and VVT controller 220 is higher than a threshold value. The communication load threshold value is a threshold value for determining whether the communication load is large enough to deteriorate the controllability of the rotation phase. In other words, the communication load threshold value is adapted so that if the communication load is equal to or less than the threshold value, it can be determined that necessary and sufficient controllability is ensured, and if the communication load exceeds the threshold value, it can be determined that there is a risk of deterioration in controllability.

[0089] If the communication load between ECM 210 and VVT controller 220 is equal to or less than the threshold, control device 230 proceeds to step S902 (rotational phase feedback control unit 212) and performs an operation to correct the target motor rotational speed of brushless motor 12 so that the actual rotational phase approaches the target rotational phase. In other words, if the communication load between ECM 210 and VVT controller 220 is equal to or less than the threshold, control device 230 controls brushless motor 12 by a combination of rotational phase feedback control unit 212 provided in ECM 210 and motor rotational speed feedback control unit 221 and motor current feedback control unit 222 provided in VVT controller 220.

[0090] On the other hand, if the communication load between ECM 210 and VVT controller 220 is higher than the threshold, control device 230 proceeds to step S903 (target relative angle calculation unit 213) and performs processing to determine the target relative angle and processing to set a request for switching to stop state control, thereby suppressing a tracking delay in the rotational phase. In other words, if the communication load between ECM 210 and VVT controller 220 is higher than the threshold, control device 230 controls brushless motor 12 by a combination of motor relative angle feedback control unit 223 and motor current feedback control unit 222 provided in VVT controller 220, without using rotational phase feedback control unit 212 provided in ECM 210.

[0091] According to this configuration, when the communication load between ECM 210 and VVT controller 220 is higher than a threshold value and the communication load between ECM 210 and VVT controller 220 could be a factor in reducing the controllability of the rotational phase, control device 230 controls the rotational phase without using rotational phase feedback control unit 212 provided in ECM 210, thereby preventing a reduction in controllability of VVT mechanism 114.

[0092] The time chart in Fig. 13 illustrates the correlation between a change in the communication load between the ECM 210 and the VVT ​​controller 220 and a request to switch the feedback control of the VVT ​​mechanism 114. At time t61 in Fig. 13, when the communication load between the ECM 210 and the VVT ​​controller 220 exceeds a threshold value, a request to switch the feedback control is generated.

[0093] Then, when a request to switch feedback control occurs, feedback control is switched from a combination of rotation phase feedback control unit 212 included in ECM 210 and motor rotational speed feedback control unit 221 and motor current feedback control unit 222 included in VVT controller 220 to feedback control using a combination of motor relative angle feedback control unit 223 and motor current feedback control unit 222 included in VVT controller 220. In other words, when the communication load between ECM 210 and VVT controller 220 becomes higher than a threshold, control device 230 reduces the number of feedback control loops used to control brushless motor 12, and performs feedback control of brushless motor 12 using motor relative angle feedback control unit 223 and motor current feedback control unit 222 included in VVT controller 220, without using rotation phase feedback control unit 212 included in ECM 210.

[0094] 13, when the communication load between ECM 210 and VVT controller 220 falls below the threshold, the request to switch feedback control is canceled. As a result, feedback control returns from the combination of motor relative angle feedback control unit 223 and motor current feedback control unit 222 provided in VVT controller 220 to feedback control using the combination of rotation phase feedback control unit 212 provided in ECM 210 and motor rotational speed feedback control unit 221 and motor current feedback control unit 222 provided in VVT controller 220.

[0095] The technical ideas described in the above embodiments can be used in appropriate combinations as long as no contradictions arise. Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that a person skilled in the art can adopt various modified embodiments based on the basic technical ideas and teachings of the present invention.

[0096] For example, the control specifications for switching feedback control in accordance with the load on brushless motor 12 are not limited to cases where control device 230 is configured by combining ECM 210 and VVT controller 220, but can also be applied to cases where brushless motor 12 is controlled by a single control device. In other words, switching feedback control in accordance with the load on brushless motor 12 can also be applied to cases where one control device (microcomputer) includes target rotational phase calculation unit 211, rotational phase feedback control unit 212, motor rotational speed feedback control unit 221, and motor current feedback control unit 222.

[0097] Furthermore, ECM 210 and VVT controller 220 form a domain architecture, which is a system structure that brings together the technical areas of electronic control devices that perform similar processing, but VVT controller 220 and a higher-level control device may also be control devices that form a vehicle-centralized zone architecture that integrates electronic control devices into the vehicle's central computer. Therefore, the higher-level control device of VVT controller 220 is not limited to ECM 210, which controls fuel injection and ignition of internal combustion engine 101.

[0098] The control device can also determine the magnitude of the processing load, such as the computational load and the communication load, and can also determine the magnitude of the load on the actuator, and switch the feedback control (change the number of feedback control loops) based on these determination results. For example, a control specification can be established in which, when the load on the actuator is high, the feedback control is switched regardless of the processing load, and when the load on the actuator is medium, the feedback control is switched only after the processing load reaches a certain level. Furthermore, the actuator using the motor can be an actuator for a variable compression ratio mechanism for an internal combustion engine, and the actuator using the motor is not limited to the VVT ​​mechanism 114.

[0099] 12...Brushless motor, 101...Internal combustion engine, 114...VVT mechanism (actuator), 210...ECM (higher-level control device), 211...Target rotational phase calculation unit, 212...Rotational phase feedback control unit, 220...VVT controller (lower-level control device), 221...Motor rotational speed feedback control unit, 222...Motor current feedback control unit, 223...Motor relative angle feedback control unit, 224...Target motor current switching unit, 230...Control device (actuator control device)

Claims

1. An actuator control device that controls an actuator that uses a motor, wherein the number of feedback control loops used to control the motor is reduced when the load on the actuator or the processing load on the control device is large compared to when the load is small.

2. An actuator control device according to claim 1, wherein the actuator changes the rotational phase of the driven rotor relative to the driving rotor according to the difference in rotational speed between the driving rotor and the motor.

3. An actuator control device according to claim 2, wherein the load on the actuator is determined based on whether the driving rotor is rotating or stationary.

4. An actuator control device according to claim 1, wherein the load on the actuator is determined based on a follow-up delay of a controlled variable relative to a target value.

5. An actuator control device according to claim 1, wherein the load on the actuator is determined based on a temperature condition of the actuator.

6. An actuator control device according to claim 1, comprising: a higher-level control device that sets a target value; and a lower-level control device that receives a control command signal based on the target value from the higher-level control device and outputs an operation amount for the motor, and the calculation load on the higher-level control device is determined as the processing load on the control device.

7. An actuator control device as claimed in claim 1, comprising: a higher-level control device that sets a target value; and a lower-level control device that receives a control command signal based on the target value from the higher-level control device and outputs an operation amount for the motor, and the communication load between the higher-level control device and the lower-level control device is determined as the processing load of the control device.

8. An actuator control device as defined in claim 2, wherein, when the load on the actuator or the processing load on the control device is smaller than a set value, the motor is controlled using a first combination of: rotational phase feedback control that determines a target motor rotational speed based on a comparison between a target rotational phase and an actual rotational phase; motor rotational speed feedback control that determines a target motor current based on a comparison between a target motor rotational speed and an actual motor rotational speed; and motor current feedback control that determines a motor operation amount based on a comparison between the target motor current and an actual motor current; and when the load on the actuator or the processing load on the control device is greater than the set value, the motor is controlled using a second combination of: motor relative angle feedback control that determines a target motor current based on a comparison between a target rotational phase change amount and an actual rotational phase change amount; and motor current feedback control that determines a motor operation amount based on a comparison between the target motor current and an actual motor current.

9. An actuator control device according to claim 8, wherein the drive rotor is a rotor that rotates in synchronization with the crankshaft of an internal combustion engine, the driven rotor is a rotor that rotates integrally with a camshaft of the internal combustion engine, and the actuator is an electric variable valve timing mechanism that changes the valve timing of the internal combustion engine by changing the rotational phase of the camshaft relative to the crankshaft.

10. An actuator control device according to claim 9, wherein the operating state of the internal combustion engine is determined to be a state in which the load on the actuator is smaller than a set value, and the motor is controlled using the first combination; and when the internal combustion engine stops, the control device determines that the load on the actuator has switched to a state in which it is larger than the set value, and switches from control of the motor using the first combination to control of the motor using the second combination.

11. An actuator control device according to claim 8, wherein the control device comprises a higher-level control device and a lower-level control device, the higher-level control device comprising: a target rotational phase calculation unit that calculates a target rotational phase, a target relative angle calculation unit that calculates a target rotational phase change amount, and a rotational phase feedback control unit that performs the rotational phase feedback control, and the lower-level control device comprising: a rotational speed feedback control unit that performs the rotational speed feedback control, a motor relative angle feedback control unit that performs the motor relative angle feedback control, a motor current feedback control unit that performs the motor current feedback control, and a target motor current switching unit that outputs either the target motor current determined by the rotational speed feedback control unit or the target motor current determined by the motor relative angle feedback control unit to the motor current feedback control unit depending on the load on the actuator or the processing load on the control device.

12. A method for controlling an actuator that uses a motor by a control device, comprising a step of reducing the number of feedback control loops used to control the motor when the load on the actuator or the processing load on the control device is large, compared to when the load is small.

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