Method for controlling the rotational speed of a motor

Abstract

A method a speed controller includes reading in an actual angular acceleration value of a motor, comparing the actual angular acceleration value to a setpoint angular acceleration value, determining a controller output torque of an integrating I-component of the speed controller based on the comparison, and controlling the rotational speed of the motor based on the determined controller output torque.

Claims

1. A method comprising a motor speed controller performing the following: determining a controller output torque of a proportional P-component of the motor speed controller; determining a deviation between an actual angular velocity of a motor and a setpoint angular velocity; multiplying the determined deviation by a quotient formed from a controller coefficient of the proportional P-component of the motor seed controller and a moment of inertia of the motor to determine a setpoint angular acceleration value of the motor; comparing an actual angular acceleration value and the setpoint angular acceleration value; determining a controller output torque of an integrating I-component of the motor speed controller based on the comparison of the actual angular acceleration value and the setpoint angular acceleration value; determining a total controller output torque of the motor speed controller from the controller output torques of the proportional P-component and integrating I-component; and controlling a rotational speed of the motor based on the determined total controller output torque.

2. The method of claim 1, wherein a characteristic curve is used for the determination of the setpoint angular acceleration.

3. The method of claim 1, wherein the setpoint angular acceleration value is determined by multiplying the deviation between the actual angular velocity and the setpoint angular velocity by a constant.

4. The method of claim 1, wherein, based on a value of the controller output torque of the integrating I-component at a first point in time, a value of the controller output torque of the integrating I-component at a second point in time is determined, the second point in time being later than the first point in time.

5. An arithmetic unit comprising processing circuitry, wherein the processing circuitry is configured to: determine a controller output torque of a proportional P-component of a motor speed controller; determine a deviation between an actual angular velocity of a motor and a setpoint angular velocity; multiply the determined deviation by a quotient formed from a controller coefficient of the proportional P-component of the motor speed controller and a moment of inertia of the motor to determine a setpoint angular acceleration value of the motor; compare an actual angular acceleration value and the setpoint angular acceleration value; determine a controller output torque of an integrating I-component of the motor speed controller based on the comparison of the actual angular acceleration value and the setpoint angular acceleration value; determine a total controller output torque of the motor speed controller from the controller output torques of the proportional P-component and integrating I-component; and control a rotational speed of the motor based on the determined total controller output torque.

6. A non-transitory computer-readable medium on which are stored instructions that are executable by a processor and that, when executed by the processor, cause the processor to perform a method, the method comprising: determining a controller output torque of a proportional P-component of a motor speed controller; determining a deviation between an actual angular velocity of a motor and a setpoint angular velocity; multiplying the determined deviation by a quotient formed from a controller coefficient of the proportional P-component of the motor speed controller and a moment of inertia of the motor to determine a setpoint angular acceleration value of the motor; comparing an actual angular acceleration value and the setpoint angular acceleration value; determining a controller output torque of an integrating I-component of the motor speed controller based on the comparison of the actual angular acceleration value and the setpoint angular acceleration value; determining a total controller output torque of the motor speed controller from the controller output torques of the proportional P-component and integrating I-component; and controlling a rotational speed of the motor based on the determined total controller output torque.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic representation of a control loop according to an example embodiment of the present invention.

DETAILED DESCRIPTION

(2) FIG. 1 shows, according to an example embodiment of the present invention, a control loop that includes a motor 2 and a speed controller 4. The motor 2 is an internal combustion engine or an electric motor of a hybrid drive for driving a motor vehicle. Speed controller 4 can be designed for controlling the idle and final rotational speed of motor 2, or can be a component of a traction control system. Speed controller 4 can be part of an arithmetic unit, for example, of an engine controller of a motor vehicle.

(3) Motor 2 includes a rotor (not shown), for example, a rotor of the electric motor or a crankshaft of the internal combustion engine. The rotor has a moment of inertia J and rotates during operation with an actual angular velocity value .sub.actual, a load torque M.sub.L being present at motor 2. Speed controller 4 is configured to regulate actual angular velocity .sub.actual to a setpoint angular velocity .sub.setpoint.

(4) As long as a controller output torque M.sub.R of speed controller 4 corresponds exactly to the applied load torque M.sub.L, no angular acceleration results, and the rotor of motor 2 rotates having a constant actual angular velocity value .sub.actual=.sub.setpoint.

(5) Changes in the angular velocity are therefore caused by a difference between controller output torque M.sub.R and load torque M.sub.L. According to the principle of angular momentum, the following applies to the time derivative of the control deviation (=(.sub.actual.sub.setpoint)) between the actual angular velocity and the setpoint angular velocity, which corresponds to an angular acceleration:
J{dot over ()}=(M.sub.RM.sub.L)(1)

(6) Therefore, motor 2 has an integrating behavior, i.e., it behaves like an integrator or like an I-element in the control loop.

(7) Controller output torque M.sub.R of speed controller 4 is composed of an integrating I-component M.sub.I and another typically proportional P-component M.sub.P:
M.sub.R=M.sub.I+M.sub.P(2)
Speed controller 4 includes an I-speed controller 4a for determining integrating I-component M.sub.I, and speed controller 4 includes a P-speed controller 4b for determining proportional P-component M.sub.P.

(8) Ideally, in such a regulating system, I-component M.sub.I compensates exactly for (continuous or static) load torque M.sub.L. Accordingly, equation (1) yields the following:

(9) $\begin{array}{cc}\stackrel{.}{}=\frac{M_R-M_I}{J}& \left(3\right)\end{array}$

(10) Therefore, this {dot over ()} ideally represents a setpoint angular acceleration value .sub.setpoint.

(11) If load torque M.sub.L is constant, other disturbances may be compensated for via P-component M.sub.P.

(12) If P-speed controller 4b is designed as a linear controller, setpoint angular acceleration value .sub.setpoint is determined by a determination unit 6 as an input value of P-speed controller 4b by multiplying angular velocity control deviation by a constant which is a quotient formed from a controller coefficient K.sub.P of proportional component M.sub.P of speed controller 4 and moment of inertia J of motor 2:

(13) ${}_{\mathrm{setpoint}}=-\frac{K_P}{J}$

(14) In the present exemplary embodiment, as a generalization, P-speed controller 4b is designed as a nonlinear controller. As an input value of P-speed controller 4b, each setpoint angular acceleration value .sub.setpoint is read out or determined from a stored characteristic curve f.sub.setpoint() by determination unit 6 for determining setpoint angular acceleration value .sub.setpoint as a function of angular velocity control deviation :
.sub.setpoint=f.sub.setpoint()
If the load remains unchanged during operation, i.e., the control loop is not disturbed by a load, load torque M.sub.L is equal to I-component M.sub.I. However, load torque M.sub.L is the largest disturbing variable in the control loop. Load torque M.sub.L may vary over a large value range in a short time, for example, due to the connection of loads such as an air conditioner or power steering of a motor vehicle, or due to changing driving resistances when coasting. In these situations, M.sub.I must preferably be rapidly adapted to the changed load. Controller output torque M.sub.I of the integrating l-component of speed controller 4 is determined based on the difference between setpoint angular acceleration value .sub.setpoint and actual angular acceleration value .sub.actual:
M.sub.I=K.sub.I(.sub.setpoint.sub.actual)dt

(15) The integrating I-component M.sub.I thus operates with integral gain K.sub.I. Within the scope of the present invention, the I-component is thus determined as a function of the deviation between the setpoint angular acceleration and the actual angular acceleration, which results in it achieving a steady-state final value (corresponding to the load torque) earlier than in the case of a determination from the control deviation between the actual angular velocity and the setpoint angular velocity.

(16) If I-speed controller 4a is designed as a nonlinear controller, a nonlinear gain g of the difference between setpoint angular acceleration value .sub.setpoint and actual angular acceleration value .sub.actual may be used:
M.sub.I=g(.sub.setpoint.sub.actual)dt

(17) If I-speed controller 4a is designed as a linear controller, controller output torque M.sub.I of integrating I-component M.sub.I of I-speed controller 4a is determined as:

(18) $M_I=-K_I\left(\frac{K_P}{J}+{}_{\mathrm{actual}}\right)dt$

(19) Integral gain K.sub.I of integrating I-component M.sub.I of I-speed controller 4a may be determined by solving this differential equation, as known per se.