The present invention contains subject matter related to and claims priority to Japanese Patent Application No. 2008-234638 filed in the Japanese Patent Office on Sep. 12, 2008, the entire contents of which being incorporated herein by reference.
1. Technical Field
The present disclosure relates to a motor controller that is suitable for controlling the drive of a motor in a relatively wide torque band.
2. Related Art
There is known, a motor drive controller where an operation member, which is touched by the hand of a user, is directly connected to a rotating shaft of a motor. The motor drive controller transmits a kinesthetic sense to the operation member by the torque of the motor (for example, see Japanese Unexamined Patent Application Publication No. 2006-197669). If a detection signal of drive current reaches a target current value while the motor drive controller drives the motor at regular intervals, the motor drive controller maintains the drive current of the motor at the target current value by performing a control that switches the state of the motor to a non-drive state.
According to the above-mentioned motor drive controller, since it may be possible to control the drive of the motor without detecting regenerative current, it is not necessary to provide a reverse-current preventing diode to each switching element. Accordingly, it may be possible to avoid an increase in the number of parts. Further, since an H-type bridge circuit is formed by using a MOSFET in a switching element, the motor drive controller has an advantage of suppressing loss during the drive in comparison with the circuit configuration that uses a bipolar transistor of a Darlington connection.
The above-mentioned motor drive controller triggers ON-signals that are generated at regular intervals and comparison output signals, and controls the switching operation of the latching H-type bridge circuit. For this reason, since the motor drive controller is superior in terms of being able to perform a constant current control without separately detecting regenerative current, the technical value thereof remains high.
In addition, the inventors have made another modification focusing on the point that the control does not effectively function unless a current detection signal is generated in the method in the related art when drive current begins to be actually supplied to the motor.
That is, since some filters (for example, bypass capacitors), which are used as countermeasures against noise, need to be provided on a feedback path of a current detection signal, there is a certain response delay in the detection signal compared with the actual drive current. For this reason, the minimum driving time when the motor should be driven is the time until the state of the motor is switched to a non-drive state by detecting that the drive current has reached a target value after the motor begins to be driven by an ON-signal. Accordingly, there is theoretically a limitation that a motor may not be driven for the time shorter that the minimum driving time in a constant current control. This limitation makes it difficult for the control to be performed in a very low torque band.
According to an aspect of the disclsoure, a motor controller includes a motor drive circuit and a control circuit. The motor drive circuit controls power to be supplied to a motor that is an object to be controlled, and switches the state of the motor to any one of a drive state and a non-drive state. If a torque instruction signal is input in a pulse width corresponding to an instruction value of torque generated in the motor, the control circuit outputs a drive signal having a pulse width, which indicates a period of time where the drive state of the motor is kept, to the motor drive circuit on the basis of the instruction value. The control circuit has the following characteristics.
The control circuit sets the maximum value of drive current supplied to the motor on the basis of the torque instruction signal. The control circuit has a constant-current control phase where the pulse width of the drive signal is defined as a period of time between the time when power begins to be supplied to the motor and the time when a value of actual drive current reaches the maximum value, and a constant-voltage control phase where the pulse width of the drive signal is defined to be equal to the pulse width of a pulse width-modulated torque instruction signal while the actual drive current of the motor does not reach the maximum value.
Embodiments of the invention will be described below with reference to drawings.
The motor drive circuit 12 controls the power to be supplied to the motor 14, and switches the state of the motor 14 to a drive state or a non-drive state. In
The control circuit 16 outputs a drive signal to the motor drive circuit 12, and controls the switching operation of the MOSFET by the motor drive circuit 12. The motor drive circuit 12 performs the switching operation on the basis of the drive signal (ON/OFF) that is input from the control circuit 16.
The control circuit 16 includes, for example, a PWM (Pulse Width Modulation) generator 18. The PWM generator 18 generates a torque instruction signal ((A) in
The control circuit 16 includes, for example, an LPF (low-pass filter) 20 at the rear end of the PWM generator 18. The LPF 20 filters the input torque instruction signal and generates a maximum value signal ((B) in
In addition, the control circuit 16 includes a comparator 22 at the rear end of the LPF 20. For example, the maximum value signal is input to a non-inverting terminal of the comparator 22. Further, a drive current detecting resistor 24 is connected to the motor drive circuit 12, and the drive current detected by the drive current detecting resistor 24 is input to an inverting input terminal of the comparator 22 as a current feedback signal ((C) in
The comparator 22 compares the input the input maximum value signal with the current feedback signal, and outputs an OFF-signal ((E) in
The control circuit 16 further includes an edge extracting unit 26, and the edge extracting unit 26 is also disposed at the rear end of the PWM generator 18. If the torque instruction signal (pulse waveform) is input to the edge extracting unit 26 from the PWM generator 18, the edge extracting unit 26 outputs an ON-signal ((D) in
A latch circuit 28 is provided at the rear end of the edge extracting unit 26 and at the rear end of the comparator 22. If an ON-signal is output from the edge extracting unit 26, the latch circuit 28 output a latch signal ((F) in
The control circuit 16 further includes an AND gate 30 that is used as an output gate of the drive signal. The torque instruction signal is input to the AND gate 30 from the PWM generator 18, and the latch signal is input to the AND gate 30 from the latch circuit 28. The torque instruction signal is input to the AND gate 30 in the waveform of an original pulse. However, the torque instruction signal is treated as a gate input signal ((G) in
For this reason, while both the torque instruction signal (gate input signal) and the latch signal are in an ON-state, the AND gate 30 outputs a drive signal ((H) in
While the drive signal is turned on, the motor drive circuit 12 supplies power to the motor 14. For this reason, a motor drive waveform ((I) in
The motor drive circuit 12 of this embodiment will be described below by means of a specific operation example.
In
(B) In
(C) In
(D) In
(E) In
(F) In
(G) In
(H) (I) in
As described above, the motor controller 10 according to this embodiment drives the motor 14 by performing a constant-voltage control phase in a relatively low torque band. Accordingly, it may be possible to generate desired torque that is instructed by the torque instruction signal.
In
(B) In
(C) In
(D) In
(E) In
(F) In
(G) In
(H) and (I) in
As described above, the motor controller 10 according to this embodiment drives the motor 14 by performing a constant-current control phase in a relatively high torque band. Accordingly, it may be possible to generate torque that is instructed by the torque instruction signal.
Any one of the two control phases of the above-mentioned control circuit 16 is naturally selected on the basis of the pulse width of the supplied torque instruction signal and the characteristics of the entire circuit, without any particular switching operations of the control phase. That is, as apparent from the circuit configuration of
Accordingly, even though the pulse width (duty ratio) of the torque instruction signal is gradually increased and the constant-voltage control phase is switched to the constant-current control phase in the control circuit 16, it may be possible to continuously perform a control without the losing of control or a torque step while the constant-voltage control phase is switched to the constant-current control phase.
In general, if drive current does not exceed the minimum current Im as shown by the I-T curve, the motor 14 is hardly driven. Meanwhile, the minimum current Im is determined by the mechanical characteristics (inertia, frictional resistance, and the like) or electrical characteristics of the motor 14. Accordingly, it is technically difficult to actually perform the constant current control of the motor 14 in a band where the drive current Id is lower than the minimum current Im (0<Id<Im). Meanwhile, as already described in “Related Art”, there is limitation such as response delay in a band where the generated torque is lower than a certain value (Ta in
In this embodiment, desired torque is generated in the motor 14 without the limitation such as the response delay by employing the constant voltage control in the torque band where the torque Td generated in the motor 14 is low (0<Td<Ta). Meanwhile, the torque of the motor 14 is simply proportional to drive voltage as shown by the V-T curve. Accordingly, in this embodiment, it might be possible to theoretically perform a control in accordance with the pulse width (>0) of the torque instruction signal even in a very low torque band (>0) close to 0.
The motor controller 10 according to this embodiment is suitably used for an operation feeling transmitting input device. That is, when a user rotates a rotatable operating shaft by a weak force, very low torque is generated in the motor 14 connected to the operating shaft. Accordingly, delicate click feeling may be transmitted to the user. This is a preferable example using the control performance of this embodiment that is excellent in the low torque band. In addition, when relatively high torque is intended to be generated in the motor, a constant-current control phase is naturally performed and constant torque may be maintained so as to follow the dynamic load change that is caused by the switching of drive voltage, a phase, or the like. Accordingly, it may be possible to make a user feel good feeling by the same amount.
The invention is not limited to the above-mentioned embodiment, and may have various modifications. The circuit configuration of the embodiment is merely a preferred example, and the invention is not limited thereto. For example, in the embodiment, logical operation has been performed using the AND gate 30. However, if the pulse widths W1 and W2 of the drive signal may be appropriately defined in the respective control phases, other logic gates may be used. In addition, the entire configuration of the control circuit 16 including the PWM generator 18 may be substituted with one-chip microcomputer or the like.
Further, the invention is not limited to the application to an operation feeling transmitting input device, and it goes without saying that the invention may be widely used for a general-purpose motor controller.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims of the equivalents thereof.
Number | Date | Country | Kind |
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2008-234638 | Sep 2008 | JP | national |