Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
  • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
  • H02P6/14—Electronic commutators
  • H02P6/16—Circuit arrangements for detecting position
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
  • G01P3/42—Devices characterised by the use of electric or magnetic means
  • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
  • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
  • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
  • G01P3/489—Digital circuits therefor

Definitions

• the invention relates to a method for determining a speed according to the preamble of patent claim 1 and a device for determining a speed according to the preamble of patent claim 5.
• a cost-effective variant consists in calculating the rotational speed with the aid of Hall sensors, a Hall sensor detecting the position of a rotor and forwarding it to a control unit.
• the Hall sensors react to the magnetic field of the rotating rotor, which consists of a magnetic material.
• To calculate the speed the time between two edges of a Hall signal is measured and the speed is calculated from it.
• the object of the invention is to provide a rapid method for determining a speed and an apparatus for carrying out the method.
• An advantage of the method according to the invention is that a speed estimate is carried out when a signal to be received from a position sensor is delayed.
• the arrival of a new position signal is delayed when the speed has decreased.
• the elapsed time since the last position signal and the arrival of the next position signal is preferably measured and compared with the last measured speed. If the time elapsed since the last position signal is greater than can be expected based on the speed, the speed is determined on the basis of the time elapsed since the last position signal.
• the difference between two previous position signals is used as the elapsed time from which a speed estimate is carried out.
• the use of the position signals means that complex conversions are not necessary. The method can therefore be carried out quickly and requires only a low computing power.
• the speed is calculated at fixed time intervals. Current speed information is thus continuously supplied.
• a counter is preferably used to calculate the elapsed time, which increments a counter value by a fixed value at fixed time intervals. The count is therefore proportional to the time compared since the last position signal.
• the speed control of the electric motor intervenes to whom the time since the last position signal is longer than it should be according to the last measured speed. Then the speed is estimated on the basis of the time that has elapsed since the last position signal. In this way, a quick and precise control of the electric motor is obtained.
• this procedure offers a safe method for DC motors with low speeds in order to obtain constant speed control. Especially with DC motors that run at low speeds, torque fluctuations can lead to unclean motor running and the motor can be excited to vibrate. If the engine swings up, for example, the engine can even stop. Because of the method according to the invention, these disadvantageous effects are reliably avoided.
• FIG. 1 shows a device according to the invention with a motor
• Fig. 2 is a diagram showing Hall signals as a function of the three phase currents and
• Fig. 3 is a schematic representation of the method according to the invention using a block diagram.
• the invention is explained below with reference to a DC motor 1, but is applicable to any type of motor.
• the DC motor is preferably in the form of a Pump motor used for electro-hydraulic power steering in a motor vehicle. With the help of the motor 1, however, any other type of device, in particular in a motor vehicle, can be controlled.
• Fig. 1 shows schematically a commutated motor 1, which is operated with direct current.
• the motor 1 has a rotatably mounted rotor 10 which, in the embodiment shown, has three magnetic poles 30, 31, 32 which are spaced apart by 120 °.
• a stator 11 is arranged around the rotor 10 and is designed in the form of magnetic coils 13, 14, 15.
• the stator 11 is connected to an output stage 12 via a supply line.
• the output stage 12 is connected to a DC voltage source 16 for controlling the first, the second and the third magnetic coils 13, 14, 15.
• the output stage 12 is connected to a control unit 5 via a control line.
• a first, a second and a third Hall sensor 2, 3, 4 are arranged on the motor 1.
• the first, the second and the third Hall sensors 2, 3, 4 are arranged around the motor 1 at equidistant angular intervals.
• the Hall sensors 2, 3, 4 serve to detect the position of the rotor 10. If a magnetic pole 30, 31, 32 of the rotor 10 moves past a Hall sensor 2, 3, 4, the magnetic field of the rotor 10 causes the Hall 10 to move Sensor generates a Hall voltage.
• the Hall voltage is forwarded to the control unit 5 via a signal line 7.
• the control unit 5 thus recognizes the local position of the rotor 10 since it knows the angular position of the first, second and third Hall sensors 2, 3, 4 in relation to a rotation of the rotor 10.
• the control unit 5 is also connected via a reset line 8 and a second signal line 9 with a counter 6 in connection.
• control device 5 controls the energization of the magnetic coils 13, 14, 15 of the stator 11.
• the interaction between the magnetic fields generated by the magnetic coils and the magnetic fields of the rotor 10 closes the rotor 10 a rotation at a desired speed.
• FIG. 2 shows a diagram in which the Hall signals of the Hall sensors 2, 3, 4 are plotted over voltage profiles of the first, second and third magnet coils 13, 14, 15.
• the diagram shows a voltage profile of the first coil 13 with Uli, the voltage profile of the second coil 14 with UI2 and the voltage profile of the third coil 15 with UI3.
• the voltage profiles are in Figure 2 because of a better one
• the first, second or third magnetic coils 13, 14, 15 are each supplied with a current with positive or negative polarity via two switching transistors T1, T2, T3, T4, T5, T6.
• the simplified A block commutation is provided, in which the solenoids 13, 14, 15 are controlled with a block-shaped current (hatched fields in FIG. 2).
• any other type of control method such as sinus commutation, can also be used.
• the magnet coils 13, 14, 15 are supplied with a clocked current signal which is essentially sinusoidal.
• a first Hall signal HS1 of the first Hall sensor 2 a second Hall signal HS2 of the second Hall sensor 3 and a third Hall signal are shown in the diagram in FIG.
• Signal HS3 of the third Hall sensor 4 is shown, which the Hall sensors 2, 3, 4 report to the control unit 5.
• the Hall signals HS1, HS2, HS3 alternate between a low level and a high level in the form of a rectangular signal. A low or high level is detected by a Hall sensor 2, 3, 4 when a north or south pole of the rotor 10 acts on the Hall sensor 2, 3, 4.
• the assignment of a high or low level to the north or south pole can be determined by a circuit evaluating the Hall signal.
• the Hall signal of the first Hall sensor 1 jumps from a low level to a high level at time t1 and from a high level to a low level at time t4.
• the times are plotted as a function of an electrical angle, 1080 ° electrical angles representing an entire revolution of the rotor 10.
• the control unit 5 usually calculates the speed of the rotor 10 with the aid of the Hall signals HS1, HS2, HS3.
• the control unit 5 uses, for example, the rising or falling edges of a Hall signal HS1, HS2, HS3.
• the control unit knows that three of the Hall sensors 2, 3, 4 are arranged around the engine 1.
• three Hall signals are generated in each Hall sensor 2, 3, 4 per revolution of the rotor.
• the rising flanks of a Hall signal from a Hall sensor thus have a time interval of 120 °, 360 ° corresponding to one revolution of the rotor 10.
• control unit 5 receives a rising edge from second Hall sensor 3.
• control unit 5 receives a rising edge from third Hall sensor 4.
• a rising edge is again generated in the first Hall sensor 2 and at time t8, a rising edge is generated again in the second Hall sensor 3.
• 3 shows a schematic illustration to explain the method according to the invention.
• the Hall sensors 2, 3, 4 give rising and falling edges of a Hall signal HS1, HS2, HS3 to the control unit 5 in the manner described.
• the control unit 5 uses an internal timer 33 to measure the time after detection a rising or falling edge of a Hall signal from a Hall sensor 2, 3, 4 passes to the next rising or falling edge of the same Hall sensor 2, 3, 4.
• the control unit 5 reads out the count of the internal timer 33 on a rising or falling edge of the same Hall signal using a capture function and calculates the speed of the rotor from the difference.
• the count of the internal timer 3 is, for example, a difference of 8,000 between two rising edges of the same Hall signal, the internal counter 33 increasing the count every 2 ⁇ s, then there is a time of 16,000 between two rising edges of the first Hall signal HS1 ⁇ s passed.
• the measured time represents one third of a revolution.
• the control unit calculates the speed U using the following formula:
• the falling edges of the Hall signals HS1, HS2, HS3 can also be used.
• the control unit 5 receives a falling edge of the first Hall signal HS1 at time t4, a falling edge of the second Hall signal HS2 at time t5 and a falling edge of the third Hall signal HS3 at time t6.
• the control unit 5 calculates the speed of the engine 1 according to the method that was explained for the rising edges.
• the timer 6 runs in parallel and is always reset when a Hall signal arrives.
• the control unit 5 starts the timer 6 on receipt of the rising edge of the first Hall signal HS1 at the time tl.
• the timer 6 counts up an internal counter in defined time stages. If the control unit 5 now receives the rising edge of the second Hall signal HS2 at the time t2, the control unit 5 stops the timer 6, reads out the count, sets the counter to the value zero and starts the timer 6 again.
• Timer 6 regardless of the capture function and the internal timer 33, captures the elapsed time since the last edge of a Hall signal. Because the Hall signals occur with a time offset, the counter reading of the timer 6 is a factor of six less than the time between two rising or falling edges of a Hall signal.
• the control unit 5 compares the last calculated speed with the elapsed time since the arrival of the last rising or falling edge. If the elapsed time is longer than it should be due to the last calculated speed, a speed calculation is carried out based on the counter reading of the counter 6. This estimation process is repeated until a rising or falling edge of a Hall signal is detected or a time-out signal arrives for a likely blocking of the motor.
• control unit 5 emits a reset signal to the counter 6 via the reset line 8 on each new edge of a first, second or third Hall signal.
• the control unit 5 continuously compares whether the counter reading of the counter 6 is greater than the time interval between the last two rising or falling edges of a Hall signal.
• the timer 6 preferably has a larger clock cycle than the internal counter 33.
• the timing is preferably in the range of 1 ms after which the timer 6 increases its counter reading.
• the speed is estimated on the basis of the counter reading of timer 6 using the following formula:
• the speed is preferably estimated at fixed time intervals, for example every millisecond.
• the new speed U is thus calculated at a count of (0.018 / n) s:
• a speed estimate is carried out every millisecond until a new capture value for a flank of a Hall signal has been recorded or until a time-out signal occurs.
• the control unit 5 preferably compares the time since the last position signal with the last measured speed. If the comparison shows that the time since the last position signal is greater than the time from which the last determined speed was derived, then the speed is estimated on the basis of the time since the last position signal. In this way, it is possible to react more quickly to fluctuations in speed or a drop in speed.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Control Of Motors That Do Not Use Commutators (AREA)

Applications Claiming Priority (5)

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• 2003
  • 2003-05-06 EP EP03735276A patent/EP1512019A1/de not_active Ceased
  • 2003-05-06 US US10/502,614 patent/US7058537B2/en not_active Expired - Fee Related
  • 2003-05-06 WO PCT/DE2003/001439 patent/WO2003100443A1/de active Application Filing
  • 2003-05-06 JP JP2004507849A patent/JP2005526982A/ja active Pending

Non-Patent Citations (1)

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