KR20100120390A - Method for searching current map of an ipmsm - Google Patents

Abstract

PURPOSE: A method is provided to improve the control frequency of IPMSM(Interior Permanent Magnet Synchronous Motor) by reducing time for executing a current map searching algorithm. CONSTITUTION: A motor velocity and a torque command is determined(S41). The motor velocity is determined whether it is between a first velocity index and a second velocity index(S42). When the motor velocity is a value between the first velocity index and the second velocity index, the torque command is determined whether it is between a first torque index and a second torque index(S46). When the torque command is a value between the first torque index and the second torque index, a current map interpolation process is executed. The first velocity index, the second velocity index, the first torque index, and the second torque index are saved(S50).

Description

{Method for searching current map of an IPMSM} for embedded permanent magnet synchronous motors

The present invention relates to a method of searching a current map of an embedded permanent magnet synchronous motor, and more particularly, to a method of searching a current map used for controlling an embedded permanent magnet synchronous motor of a hybrid vehicle.

An embedded permanent magnet synchronous motor (IPMSM) is a synchronous motor in which permanent magnets are inserted inside the rotor core. This embedded permanent magnet synchronous motor has excellent high speed durability and high driving speed, making it suitable for use as a motor for hybrid vehicles.

Embedded permanent magnet synchronous motors can achieve high power density due to the additional presence of reluctance torque and parametric nonlinearity. The permanent magnet synchronous motor is preferably controlled so that the motor current is set so that the combined torque of normal electromagnetic torque and its unique reluctance torque is maximum, and the maximum torque per unit current is output.

In the conventional permanent magnet synchronous motor control method, the control amount is calculated based on the model of the motor, and control is performed based on this. However, the control method based on the model of the motor has a problem that performance is uneven and control accuracy is lowered because an error occurs in the calculation result due to nonlinearity of the motor parameters.

In order to solve this problem, a method is proposed to extract the optimal motor current value corresponding to the engine speed and torque command value by experiment, and to control the permanent magnet synchronous motor based on this current map. It became.

Korean Patent Application Publication No. 2006-42282, `` Optimal Current Map Extraction Method for Embedded Permanent Magnet Synchronous Motor, '' discloses a method of extracting a current map that can be efficiently optimized for embedded permanent magnet synchronous motors (synchronous motors). do.

As can be seen in the above prior patent, the current map, as shown in Figure 1, the X-axis is the speed and the Y-axis is the torque command, it is made of a matrix form of (n + 1) * (m + 1). The current map interpolation function is the input of motor speed and torque command, and the output is D-axis current and Q-axis current. A separate current map exists for each of the driving region shown in FIG. 1A and the power generation region shown in FIG. 1B, and a current map of the D-axis current and the Q-axis current for each region, respectively. This exists separately.

The most common method of searching current values by the speed and torque command of a motor is the binary searching method. This binary search method finds a target point while dividing an arbitrary section into two parts, as shown in FIG.

3 is a diagram illustrating a current map search method using a binary search method. The final current command value is searched by performing binary search on the current map in the X-axis direction and Y-axis direction, respectively.

Embedded permanent magnet synchronous motors applied as hybrid motor drive motors or generators require high-speed control cycles. In general, the control period of the motor or generator is about 20 times the maximum rotation frequency respectively. For example, precision control of an 800Hz permanent magnet synchronous motor would ideally require a control cycle of around 16kHz. However, this control period is limited by the limitations of the performance (computation speed, memory, etc.) of the microcomputer used.

Typical current maps have limited fast computational control for the following reasons: In general, since motor motors have different characteristics depending on the low / high speed section and the low torque / high torque section, reference values of speed and torque, which are inputs of the current map, are formed at boiling intervals during current mapping. For example, the speed intervals are formed at boiling intervals such as 500, 1000, 1200, 1500, 2000, 3000, 4000, 5000, 5500, 6000, and the torque command is 5, 10, 15, 20, 30, 40, .. ., 90, 105, 110, 115, 120, etc. are formed at boiling intervals. As such, the characteristics of the boiling interval map element of the current map make it impossible to use the fast search operation such as the use of a pointer in the equally spaced map search widely used as a software technique. In addition, as the number of current maps is finely divided and the number of current maps is increased, the accuracy of control and the efficiency of the system are increased, but the searching time of the microcomputer according to the current map search becomes longer.

That is, conventionally, the computation time for the microcomputer to search the current map is long, and therefore, there is a problem that precision control and performance are limited.

SUMMARY OF THE INVENTION An object of the present invention devised to solve the above problems of the prior art is to provide a current map search method of an embedded permanent magnet synchronous motor, in which a time for performing a current map search algorithm is shortened, thereby increasing the synchronous motor control frequency. It is for.

The current map search method of the embedded permanent magnet synchronous motor according to the present invention for achieving the above object, the initial value of the first speed index and the second speed index adjacent to each other in the previous current map search step, and adjacent to each other A first step of receiving initial values of the first torque index and the second torque index;

A second step of searching for a new first speed index and a new second speed index to which the current motor speed belongs by using the first speed index and the second speed index;

A third step of searching for a new first torque index and a new second torque index to which the current torque command belongs by using the first torque index and the second torque index;

Performing current map interpolation on the new first speed index and the new second speed index found in the second step and the new first torque index and the new second torque index found in the third step; And a fourth step of providing the new first torque index and the new second speed index and the new first torque index and the new second torque index as initial values of the next current map search step.

As described above, according to the present invention, the time for performing the current map search algorithm is shortened, so that the control frequency of the synchronous motor is increased. As a result, precision control and performance improvement of the synchronous motor are increased, and efficiency is improved.

Hereinafter, a current map search method of an embedded permanent magnet synchronous motor according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Before describing an embodiment of the present invention, a driving principle of the present invention will be described.

The control of the synchronous motor is high speed control over several kHz. For example, a system with a 10 kHz control bandwidth controls a motor at 100 us periods. However, the variation in the speed at which the actual motor changes over 100us is very small. In addition, similarly to torque, even if the torque command value changes significantly, the amount of torque conversion is limited to a predetermined value or less for the stability of motor control. On the other hand, the torque command is transmitted through the communication from the upper controller, and considering that the communication period is usually several tens of ms or more, it can be seen that the amount of torque change is very small during the motor control period of 100us.

For these reasons, the speed and torque of the motor used in the previous search phase do not change much in the current search phase. Equation 1 is the acceleration of the motor (a = dv / dt), the change rate of the torque command (dT / dt), the control frequency (f), the component interval of the current map (V _n -V _n-1 , T _n -T _n-1 ).

For example, when the speed of the current map is 100rpm and the torque interval is 5Nm, the acceleration (a = dv / dt) and the torque change rate (dT / dt) of the applicable synchronous motor are as follows. .

f = 100 kHz, A = 100 rpm, B = 5 Nm

a = dv / dt = 10000 * 100 rpm / sec = 1,000,000 rpm / sec = 1000 rpm / msec

dT / dt = 10000 * 5 Nm / sec = 50000 Nm / sec = 50 Nm / msec

That is, if the synchronous motor does not exceed the acceleration of 1000 rpm per msec and the torque change rate does not exceed 50 Nm per msec, this invention can be applied. In general, the synchronous motor is connected to the engine to drive and generate power, so the acceleration of the motor is the acceleration of the engine. Engines with acceleration and torque change rates above are practically impossible. That is, the present invention can be applied to all synchronous motors.

In the conventional binary search, a search start point is always designated as a fixed point (origin or reference point), and it takes a long time to search for a target point from the search start point. In the present invention, the search time is shortened by setting the search start point to the motor speed and torque command used in the previous search.

In addition, in the case of the conventional binary search, the search direction always proceeds in the same direction. In contrast, in the present invention, the search is started in a direction in which the speed and torque command of the motor are changed in the current search step compared to the previous search step. That is, if the motor is accelerating, the search starts in the acceleration direction, and if the motor is decelerated, the search starts in the deceleration direction.When the torque command increases, the search starts in the increase direction, and when the torque command decreases, the search starts in the decrease direction. To start.

4 is a flowchart illustrating a method of searching a current map of an embedded permanent magnet synchronous motor according to an exemplary embodiment of the present invention.

First, when the vehicle is turned on, the speed index (speed_id) and torque index (torque_id) are initialized. The first speed index (speed_id (1)) and the first torque index (torque_id (1) are initialized. )) Is set to 0, and the second speed index (speed_id (2)) and the second torque index (torque_id (2)) are set to 1.

When the current map search starts, the motor speed and torque command are determined (S41). First, the speed index (velocity_id) search process is performed. If the motor speed determined in step S41 is a value between the first speed index (speed_id (1)) and the second speed index (speed_id (2)) (S42), the process proceeds to step S46 to determine the torque index (torque_ id) Perform search.

If the motor speed determined in step S41 is not a value between the first speed index (speed_id (1)) and the second speed index (speed_id (2)) (S42), it is determined whether the motor speed is increasing ( S43). If the motor speed is increasing in step S43, the first speed index (speed_id (1)) and the second speed index (speed_id (2)) are each increased by 1, and if the motor speed is not increasing, the first speed is increased. After decreasing the index (speed_id (1)) and the second speed index (speed_id (2)) by 1, the process returns to step S42 and the motor speed is equal to the first speed index (speed_id (1)). Steps S42 to S45 are repeated until the value between the second speed indexes (speed_id (2)) is reached.

If the motor speed determined in step S41 is a value between the first speed index (speed_id (1)) and the second speed index (speed_id (2)) (S42), the torque command determined in step S41 is the first torque. It is determined whether the value is between the index (torque_id (1)) and the second torque index (torque_id (2)) (S46). If it is determined in step S46 that the torque command is not a value between the first torque index (torque_id (1)) and the second torque index (torque_id (2)), it is determined whether the torque command is increasing (S47). . If the torque command is increasing in step S47, the first torque index (torque_id (1)) and the second torque index (torque_id (2)) are each increased by 1, and if the torque command is not increasing, the first torque is increased. After decreasing the index (torque_id (1)) and the second torque index (torque_id (2)) by 1 (S49), the process returns to step S46 and the torque command is the first torque index (torque_id (1)). )) And steps S46 to S49 are repeated until the value is between the second torque index (torque_id (2)).

If the torque command determined in step S41 is a value between the first torque index (torque_id (1)) and the second torque index (torque_id (2)) (S46), current map interpolation is performed, and the first speed is performed. Store index (speed_id (1)), second speed index (speed_id (2)), first torque index (torque_id (1)) and second torque index (torque_id (2)) (S50). This ends the current map search.

When the current map is searched in the next step, step S41 is performed based on the stored speed_id (1), speed_id (2), torque_id (1) and torque_id (2).

1 is a diagram illustrating a general current map, in which (a) is a current map of a driving region, (b) is a current map of a power generation region,

2 is a diagram illustrating a general binary search method;

3 is a diagram illustrating a current map search method applying a general binary search method;

4 is an operation flowchart illustrating a current map search method according to an embodiment of the present invention.

Claims (3)

A first step of receiving initial values of the first speed index and the second speed index adjacent to each other and a first value of the first torque index and the second torque index adjacent to each other in the previous current map search step; A second step of searching for a new first speed index and a new second speed index to which the current motor speed belongs by using the first speed index and the second speed index; A third step of searching for a new first torque index and a new second torque index to which the current torque command belongs by using the first torque index and the second torque index; Performing current map interpolation on the new first speed index and the new second speed index found in the second step and the new first torque index and the new second torque index found in the third step, And a fourth step of providing the new first torque index and the new second speed index and the new first torque index and the new second torque index as initial values of the next current map search step. Current map search method of permanent magnet synchronous motor. The method of claim 1, wherein the second step comprises: increasing the first speed index and the second speed index by one when the motor speed is increasing, and increasing the first speed index and the second speed index when the motor speed is not increasing. And searching for the new first speed index and the new second speed index by decreasing the speed index by one. The method of claim 1, wherein the third step includes increasing the first torque index and the second torque index by one when the torque command is increasing, and increasing the first torque index and the second torque index by one when the torque command is not increasing. The current index search method of the embedded permanent magnet synchronous motor, characterized in that for reducing the torque index by one, to search for the new first torque index and the new second torque index.

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