MOTOR CONTROL
Firmware User Guide: Low Voltage BLDC Motor Control
using SAM Devices
USER GUIDE
LV Kit
Introduction
This user guide covers the firmware configuration details of motor control algorithms. The algorithms are
Field Oriented Control (FOC) and Block Commutation (BC). Currently, the scope of the document takes
care of FOC with sensorless operation and BC with HALL sensor operation. The supported controller is
SAM D21.
Features
FOC (Field Oriented Control) – Sensorless
BC (Block Commutation) – Hall sensor
Atmel® Start usage
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
Ta bl e of Conte nts
1
FOC Sensorless ........................................................................................................... 3
1.1
1.2
1.3
1.4
2
BC HALL ................................................................................................................... 11
2.1
2.2
2.3
2.4
2.5
LV Kit .............................................................................................................................................. 11
Configuration Parameters.................................................................................................................... 11
Identification and Changing of PINS .................................................................................................... 13
To Run a Different Motor with BC-HALL.............................................................................................. 13
PWM Frequency.................................................................................................................................. 15
3
BC HALL via Atmel Start ........................................................................................... 16
4
FOC Sensorless – Startup ......................................................................................... 18
4.1
4.2
2
HV and LV Kit ........................................................................................................................................ 3
Configuration Parameters...................................................................................................................... 3
Identification and Changing of PWM Pins ............................................................................................. 8
Steps to Make PWM and Sampling Frequency Same ........................................................................... 8
Principles ............................................................................................................................................. 18
Startup Procedure ............................................................................................................................... 18
5
ATMEL EVALUATION BOARD/KIT IMPORTANT NOTICE AND DISCLAIMER ........ 21
6
Revision History ........................................................................................................ 22
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
2
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
1
FOC Sensorless
The following sections explain the firmware configuration for FOC sensorless solution.
1.1
HV and LV Kit
In the file motor_control_defs.h, ensure the following is done to use the LV (low voltage kit) kit. Ensure
that SAMHVDRIVE is disabled and ATBLDC24V is enabled. The default kit motor is M42BL024042 and
the set of parameters is defined in the same file. All the parameters are explained in Section 1.2.
Table 1-1.
LV Kit
Code listing in motor_control_defs.h
#define M42BL02402
/* 42BL02402-0026B-002 motor */
#define ATBLDC24V
/*#define SAMHVDRIVE*/
/* low voltage demo */
/* high voltage demo */
If the HV (High Voltage) kit should be used then the following has to be done. Ensure that the macro
ATBLDC24V is commented and SAMHVDRIVE is enabled.
Table 1-2.
HV Kit
Code listing in motor_control_defs.h
/* #define ATBLDC24V */
/* low voltage demo */
#define SAMHVDRIVE
/* high voltage demo */
Similarly add a suitable name for the motor as a #define and define all the equivalent parameters given in
Section 1.2.
1.2
Configuration Parameters
Table 1-3.
PWM_HPER_TICKS
Properties
Description
Name
PWM_HPER_TICKS
Units
Number
Description
PWM frequency used to control the motor.
Remarks
MCU frequency is kept at 48MHz, i.e. 48 PWM ticks corresponds to 1µs. To achieve a frequency of 6kHz (period of 166.67µs), 8000 PWM ticks is required. Centre aligned PWM is
used hence half of the required ticks is used here.
Similarly to achieve PWM frequency of 10kHz (period of 100µs), 4800 PWM ticks is required.
(Macro would hold 2400.)
Formula:
PWM_HPER_TICKS = (MCU_FREQ_HZ) / (REQUIRED_FREQ_HZ * 2)
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
3 3
Table 1-4.
START_SPEED_DEFAULT
Properties
Name
START_SPEED_DEFAULT
Units
RPM
Description
Default start up speed in rpm
Remarks
The motor’s initial startup speed and the value will also be displayed in the GUI for usage
Table 1-5.
POLAR_COUPLES
Properties
Description
Name
POLAR_COUPLES
Units
Number
Description
Number of pole pairs in a motor
Remarks
None
Table 1-6.
MIN_FRE_HZ
Properties
Description
Name
MIN_FRE_HZ
Units
Hertz
Description
Minimum frequency supported by the motor
Remarks
This value is used in radians per second within the code, for instance if the minimum frequency is 50Hz, this is realized as 314 rad per sec (2 * PI * freq.). The same in rpm would be
(frequency * 60 / POLAR_COUPLES)
Formula:
Angular frequency (Ѡ) = 2 * PI * MIN_FRE_HZ
Minimum RPM
= (MIN_FRE_HZ * 60) / PO-LAR_COUPLES
Table 1-7.
MAX_FRE_HZ
Properties
4
Description
Description
Name
MAX_FRE_HZ
Units
Hertz
Description
Maximum frequency supported by the motor
Remarks
Scaling factor: 1 rpm is represented as 1 * 16384 / MAX_RPM in the code. For example if
maximum rpm is 6000 then 1 rpm would be 2.73. By integer division it would be 2. Essentially
the maximum frequency supported by the motor plays role in resolution of the speed. Enter
the value appropriate to the motor specification.
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
4
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
Table 1-8.
R_STA
Properties
Description
Name
R_STA
Units
Ohm
Description
Stator Phase Resistance
Remarks
If the data sheet has provided line-to-line resistance, the value can be divided by 2
Table 1-9.
L_SYN
Properties
Description
Name
L_SYN
Units
Henry
Description
Synchronous inductance
Remarks
Value in general it is one or two times of the phase self-inductance
Table 1-10.
MAX_CUR_AMP
Properties
Description
Name
MAX_CUR_AMP
Units
Amperes
Description
Maximum current that can be allowed to the motor
Remarks
Used in the speed PI loop for limit check
Table 1-11.
START_CUR_AMP
Properties
Description
Name
START_CUR_AMP
Units
Amperes
Description
Peak Start up current
Remarks
During the speed ramp, in ALIGN state the “d” current is ramped up to this configuration
value
Table 1-12.
ACC_RPM_S
Properties
Description
Name
ACC_RPM_S
Units
Rpm per second
Description
Acceleration ramp
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
5 5
Properties
Remarks
Table 1-13.
During the speed ramp, allowed rpm per second is given here. This value is sampled down to
10ms and added to absolute speed during ramp. As explained earlier the scaling factor given
for rpm is taken care with a derivative macro.
DEC_RPM_S
Properties
Description
Name
DEC_RPM_S
Units
Rpm per second
Description
Deceleration ramp
Remarks
During the speed ramp descent, allowed rpm per second is given here. Similar to acceleration, deceleration is done.
Table 1-14.
KP_V_A
Properties
Description
Name
KP_V_A
Units
Volt / Ampere
Description
Current loop proportional gain
Remarks
Same gain is used in both Iq and Id current control
Table 1-15.
KI_V_AS
Properties
Description
Name
KI_V_AS
Units
Volt / (Ampere * Sec)
Description
Current loop integral gain
Remarks
Same gain is used in both Iq and Id current control
Table 1-16.
KP_AS_R
Properties
6
Description
Description
Name
KP_AS_R
Units
Amp / (rad/sec)
Description
Speed loop proportional gain
Remarks
Speed loop Kp value
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
6
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
Table 1-17.
KI_A_R
Properties
Description
Name
KI_A_R
Units
Amp / ((rad/sec) * sec)
Description
Speed loop integral gain
Remarks
Speed loop Ki value
Table 1-18.
STUP_ACCTIME_S
Properties
Description
Name
STUP_ACCTIME_S
Units
Sec
Description
Startup acceleration time
Remarks
In STARTING state, the time taken to reach the MINIMUM speed
Table 1-19.
CUR_RISE_T
Properties
Description
Name
CUR_RISE_T
Units
Sec
Description
Current rising time during start up alignment
Remarks
The time required to reach the START_CUR_AMP in ALIGN state
Table 1-20.
CUR_FALL_T
Properties
Description
Name
CUR_FALL_T
Units
Sec
Description
Direct current falling time after startup
Remarks
During RUNNING state the time required to ramp down the “d” current
Table 1-21.
SAMPLING_FREQUENCY
Properties
Description
Name
SAMPLING_FREQ
Units
Hertz
Description
Sampling frequency of the motor control loop:
0.25 * MCU_FREQ_HZ / PWM_HPER_TICKS.
(Half of PWM frequency, value is represented in Hertz. To maintain the sampling frequency
same as PWM frequency, multiply it by 0.5 instead of 0.25.)
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
7 7
Properties
Remarks
1.3
Description
The general notation followed is to maintain the sampling frequency same as PWM frequency. If PWM frequency is 10kHz then sampling frequency should also be kept at the same
value.
However due to additional application requirements it’s not possible to accommodate all the
routines within the PWM control loop. Hence the sampling frequency is kept at half of the
PWM control frequency.
Identification and Changing of PWM Pins
We need six PWM pins and four ADC pins to run the FOC sensorless solution. The six PWM pins are
fixed in the board and the same can be changed in the workspace (if required). The pins can also be
changed in the Atmel start.
WO_0 ,WO_1,WO_2 refers to high side PWM pins of phase A, B, and C respectively. WO_4, WO_5,
WO_6 refers to the low side PWM pins of phase A, B, and C respectively.
Table 1-22.
Code Listing PWM Pins
Code listing in atmel_start_pins.h
#define
#define
#define
#define
#define
#define
PWM_WO_0
PWM_WO_1
PWM_WO_2
PWM_WO_4
PWM_WO_5
PWM_WO_6
GPIO(GPIO_PORTA,
GPIO(GPIO_PORTA,
GPIO(GPIO_PORTA,
GPIO(GPIO_PORTA,
GPIO(GPIO_PORTA,
GPIO(GPIO_PORTA,
8)
9)
10)
14)
15)
16)
Similarly ADC pins can also be changed in the same file.
1.4
Steps to Make PWM and Sampling Frequency Same
The solution that is provided by default has PWM frequency at 6kHz and motor control loop sampling
frequency at 3kHz. In general this is sufficient to turn the motor with good efficiency, but in case there is a
need to change the motor control loop sampling frequency to the same as PWM frequency (6kHz) the
following should be done.
Table 1-23.
Change in Following Files
Steps
8
Description
Name
SAMPLING_FREQ
motor_control_defs.h
Change #SAMPLING_FREQ# to the following definition:
0.5 * MCU_FREQ_HZ / PWM_HPER_TICKS
Function: adc_result_ready
In the function adc_result_ready – triggered ADC channel should be pointed to the
phase current channel and DC bus voltage should be measured using polling
method. Refer Table 1-24.
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
8
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
Table 1-24.
Code Listing adc_result_ready
Code listing in adc_result_ready
void adc_result_ready(const struct adc_module *const adc_inst)
{
if (0U == adc_interrupt_counter)
{
adc_interrupt_counter = 1;
/* store the first ADC result value */
cur_mea[phaseindex[1]] =
((int16_t)adc_result_data (int16_t)adc_calibration[phaseindex[1]]);
/* select the next adc channel */
adc_select_channel(adc_channel_pins[phaseindex[2]]);
/* start the conversion */
/*lint -e9078 -e923 */
ADC->SWTRIG.reg |= (uint8_t)ADC_SWTRIG_START;
/*lint +e9078 +e923 */
}
else
{
/*lint -save -e9078 -e923 */
/* MISRA 11.4, 11.6 VIOLATION */
/* register access */
adc_interrupt_counter = 0U;
/* store the second ADC result value */
cur_mea[phaseindex[2]] =
((int16_t)adc_result_data - (int16_t)adc_calibration[phaseindex[2]]);
/* Both current ADC channel results are now ready: let's read
the BUS voltage (via polling) */
/* Disable the ADC interrupt */
adc_disable_interrupt(adc_inst->hw,ADC_INTERRUPT_RESULT_READY);
/* select the right channel */
adc_select_channel((uint16_t)MOTOR_PHASE_DC_VOLTAGE_PIN);
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
9 9
Code listing in adc_result_ready
/* start the conversion */
ADC->SWTRIG.reg |= (uint8_t)ADC_SWTRIG_START;
/* something can be done while waiting for end of conversion */
current_measurement_management();
/* check if conversion is finished */
while (0U == ADC->INTFLAG.bit.RESRDY)
{
/* wait for conversion to finish */
}
/* clear interrupt flag */
ADC->INTFLAG.reg = ADC_INTFLAG_RESRDY;
/* store ADC result in variable */
while ((ADC->STATUS.reg & ADC_STATUS_SYNCBUSY) > 0U)
{
/* Wait for synchronization */
}
adc_dc_bus_voltage = ADC->RESULT.reg;
/* motor control */
motorcontrol();
/* select the next channel */
adc_select_channel((uint16_t)adc_channel_pins[phaseindex[1]]);
/* Enable the interrupt */
adc_enable_interrupt(ADC,ADC_INTERRUPT_RESULT_READY);
/*lint -restore */
}
return;
}
10
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
1
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
0
2
BC HALL
The following section explains the HW and firmware configuration of Low voltage Kit.
2.1
LV Kit
The BC-HALL algorithm is supported only in Low Voltage Kit. For the complete connections, refer the kit
manual.
The default motor used in LDO and the same define can be seen in block_commutation_cfg.h file.
Table 2-1.
Motor Define
Code listing in atmel_start_pins.h
#define M42BL02402
2.2
1
Configuration Parameters
Table 2-2.
MOTOR_POLE_PAIRS
Properties
Description
Name
MOTOR_POLE_PAIRS
Units
Number
Description
Number of pole pairs for the given motor
Remarks
Available in any given motor data sheet, for the kit motor the value is 4
Table 2-3.
SPEED_KP_DEFAULT
Properties
Description
Name
SPEED_KP_DEFAULT
Units
Number (proportional gain). The unit can also be realized as (1 / rpm).
Description
Speed pi control proportional gain
Remarks
The value can also be changed via data visualizer in run time. The given PI control converts
the given speed to an equivalent duty cycle. The gain is scaled by a factor of 64.
Table 2-4.
SPEED_KI_DEFAULT
Properties
Description
Name
SPEED_KI_DEFAULT
Units
Number (proportional gain). The unit can also be realized as (1 / (rpm * minutes))
Description
Speed PI Integral gain
Remarks
The value can also be changed via data visualizer in run time. The given PI control converts
the given speed to an equivalent duty cycle.
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
11 1
1
Table 2-5.
START_SPEED_DEFAULT
Properties
Name
START_SPEED_DEFAULT
Units
Rotations per Minute (RPM)
Description
When the motor starts the motor starts from the given reference speed
Remarks
NA
Table 2-6.
SPEED_DEFAULT_DUTY
Properties
Description
Name
SPEED_DEFAULT_DUTY
Units
Number (ticks) with reference to period ticks
Description
The period is put at 2400 (50µs). A default value of duty cycle is required for the startup.
Remarks
As a thumb rule this value could be approximately 10% of the period and a relevant startup
speed should be provided
Table 2-7.
MOTOR_MINIMUM_SPEED
Properties
Description
Name
MOTOR_MINIMUM_SPEED
Units
RPM
Description
The minimum speed of the motor
Remarks
This value is used within DV for restriction purposes
Table 2-8.
MOTOR_MAXIMUM_SPEED
Properties
Description
Name
MOTOR_MAXIMUM_SPEED
Units
RPM
Description
The maximum speed of the motor
Remarks
This value is used within DV for restriction purposes
Table 2-9.
MOTOR_RAMPUP_SPEED_PER_MS
Properties
12
Description
Description
Name
MOTOR_RAMPUP_SPEED_PER_MS
Units
RPM/ms (millisecond)
Description
During the change of speed, the ramp for the rpm to be provided in ms units
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
1
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
2
Properties
Remarks
Description
Assuming the motor wants to change from 2000 to 2500 rpm, a value of 1 in this column, will
make the system to take 500ms to achieve 2500 rpm from 2000 rpm. A value of 0 would imply an instant jump from 2000 to 2500.
The macro MOTOR_MAXSPEED_TARGET is not used anywhere.
2.3
Identification and Changing of PINS
Changing of PWM pins is similar to section given in FOC (1.3).
Hall Pins:
Though the HALL pins can also be changed in a similar way as the PWM pins but there is a hard
reference done within the code, so the user has to be extra cautious if a change of pin is desired.
Appropriate pins and register should be changed in the functions motor_start and update_communication.
Currently this is practiced for optimization reasons.
Table 2-10.
Hall Pins Changes Within Motor Control
Code listing in motor_start and update_communication
curhall1 = (uint8_t)((REG_PORT_IN0 & 0x00000008U)>>1U);
curhall2 = (uint8_t)((REG_PORT_IN0 & 0x00040000U)>>17U);
curhall3 = (uint8_t)((REG_PORT_IN0 & 0x10000000U)>>28U);
2.4
To Run a Different Motor with BC-HALL
Block commutation principle demands two significant changes within TCC peripheral to turn a motor.
1.
Hall sensor pattern.
2.
Commutation pattern.
Sample motor patterns are provided within the given code base. However, if a new motor is provided,
following should be done.
Hall sensor pattern
We know that the hall sensors is three wired and grey coded. To optimize the implementation the
following is done within the code. Typical Hall sensor pattern would move in the following way:
1(001) → 3 (011) → 2 (010) → 6 (110) → 4 (100) → 5 (101) → 1(001)
Assuming we read 1 as the valid Hall signal, the software should have the ability to know that the next
pattern would be 3. Hence an array of 16 bytes is created, in the array index of 1, value 3 is stored.
Similarly, if the hall sensor signal is 6, in the array index of 6 the value 4 is stored, which would be the
next hall pattern. Refer Table 2-11 for the pattern.
Array index 1 to 6 is used for CW (clock wise rotation) and 9 to 14 is used for CCW (counter clock wise).
Array index 0, 7, 8, and 15 will be unused.
Table 2-11.
Hall Sensor Pattern
Code listing in motor_control.c
static const uint8_t HALL_ARRAY[16] = { 0, 3, 6, 2, 5, 1, 4, 0, 0, 5, 3, 1, 6, 4, 2, 0 };
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
13 1
3
Commutation pattern
For every Hall sensor pattern read, equivalent commutation pattern should be applied to the TCC
peripheral the same is stored in the variable COMMUTATION_ARRAY.
To understand the pattern, let’s analyze one value. We are giving the PWM to high side and a simple
ON/OFF switch to low sides. All the low side switches should be OFF so that there is no PWM supplied.
All High side switches should be switched ON/OFF depending on the hall state. This is determined in the
lower two nibbles.
The higher two nibbles determine the value of output line if there is no PWM is supplied to that pin.
Example: 0x4075. Here the commutation is to supply PWM to phase B (Phase V) and make the low side
of Phase C (phase W) high. The rest is not supplied anything. A value of 1 in pattern output enable stops
the PWM and the output line state is determined by equivalent pattern output value.
14
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
1
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
4
Table 2-12.
Commutation Pattern
Code listing in motor_control.c
const uint16_t COMMUTATION_ARRAY[16] = {
0,
/* to achieve C+ B-, put the following in Pattern register H1H2H3: 001 */
0x4075, //0x4075, HS //0x0237U, LS
/* to achieve B+ A-, put the following in Pattern register H1H2H3: 010 */
0x2076, //0x2076, HS //0x0157U, LS
/* to achieve C+ A-, put the following in Pattern register H1H2H3: 011 */
0x4076, //0x4076, HS //0x0137U, LS
/* to achieve A+ C-, put the following in Pattern register H1H2H3: 100 */
0x1073, //0x1073, HS //0x0467U, LS
/* to achieve A+ B-, put the following in Pattern register H1H2H3: 101 */
0x1075, //0x1075, HS //0x0267U, LS
/* to achieve B+ C-, put the following in Pattern register H1H2H3: 110 */
0x2073, //0x2073, HS //0x0457U, LS
/* Not a valid pattern */
0,
0,
0x2073,
0x1075,
0x1073,
0x4076,
0x2076,
0x4075,
0
};
2.5
PWM Frequency
The PWM frequency provided is 20kHz (50ms time period). If a change is needed the following line
should be changed. The clock is set at 48MHz, and edge aligned PWM is used. 48 ticks would
correspond to 1ms.
Table 2-13.
PWM Frequency
Code listing in motor_control.c – function (motor_pwm_init)
pwm_set_parameters(&PWM_MOTOR_DRIVER, 2400, 240);
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
15 1
5
3
BC HALL via Atmel Start
1.
Go to http://start.atmel.com/.
2.
The following web page would appear. Select BLDC Low voltage kit and click “Browse All
Examples”.
Note:
Don’t use Create New Project as the dependencies are high and user had to take care of it.
Figure 3-1.
3.
The list of examples supported for the kit are loaded.
Figure 3-2.
4.
16
Browse Project
Select Example Project
On clicking “Open”, the application is loaded in START.
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
1
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
6
Figure 3-3.
5.
Note:
“EXPORT PROJECT” button opens the application pack download page, by clicking the
“DOWNLOAD PACK” button, the application ATZIP file can be downloaded.
Only the Atmel Studio project download is supported.
Figure 3-4.
6.
List of Components in the Example Application
List of Components in the Example Application
Open the download .atzip file in Atmel Studio 7, which will open the project creation dialog. The
complete working application will be created through the dialog.
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
17 1
7
4
FOC Sensorless – Startup
The basic FOC block diagram is well known and given below.
4.1
Principles
It’s a reference system in which the variables which allow us to control the system are DC quantities
(slowly varying in the time) rather than sinusoidal
This allows the use of the classical PI controllers
It is not important which variables are controlled through the PI controllers, but only the fact that we
are working in a rotating reference system, which allows us to see these variables as DC quantities
The classic FOC scheme provides the control of the stator currents, seen from a reference system
which is linked to the permanent magnets flux m (rotor)
Another possible choice is to orientate the rotating system as the total stator flux
d Ld id m
q Lq iq
4.2
Startup Procedure
This is a generic startup procedure that could be used to turn motors.
18
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
1
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
8
When the motor is stopped the position is usually unknown. The bemf observer cannot work when the
speed is lower than a minimum value which is determined by the motor and the application. From this
comes the necessity of an open loop acceleration procedure, which allows the motor to reach the
minimum speed at which the observer can work correctly; at this point the speed loop can be closed and
the control assumes the form already described in the block scheme.
Since the effective position is not known, we will use an arbitrary position for our (d, q) reference system;
this means that the quantities which are referred to d-quantity or q-quantity in this process will not have
any determined relationship with the rotor position, till when the speed loop will be closed.
Let's start with angle zero: our rotating reference system is aligned with (, ) system and it is stopped. In
sequence, we will perform the following operations:
Increase the current reference at zero speed (that is keeping constant the position). This will
produce a current vector with a constant argument (for simplicity, d reference is chosen to zero).
When (and if) the current amplitude will be large enough, the rotor will tend to align to the current
vector direction. The effective rotor position will depend on the starting position and on the load.
When reached a current vector amplitude which is retained enough (depending on the application,
this value can be equal to the maximum allowable current), we begin to change the current vector
position. This is obtained keeping constant the current references, but changing the reference
system position. The speed is increased linearly, and the position is obtained integrating the speed.
In this acceleration process the real position of the rotor in respect to our reference system is still
uncertain, so it is unknown how the current vector is divided into torque and flux components.
During the acceleration process, the bemf observer works. When the speed is high enough, and
after a minimum settling time, the observer will be more or less aligned with the real system, so the
position of the system becomes known.
When the speed is retained high enough and the observer settling time is elapsed, it comes the
moment to close the speed loop. This means that we should align our reference system position
with the rotor position, estimated with the bemf observer. Here the problem lies in the memories of
the current PI controllers, which are referred to the actual arbitrary (d, q) system. The integral
memories of the current PI controllers are voltages, referred to the actual rotating system, so the
first operation to do is to refer them to the static (, ) system with a Park inverse transformation,
then to refer them to the new (d, q) reference system position with a direct Park transformation,
performed after having update the angle. The same operations are needed for the current
references, in order to avoid any discontinuity in the transition.
From now, in advance, the normal closed loop speed control can be performed, so the q current
reference will be determined by the speed control loop, while the d current reference, which is still
present, can be gradually reduced to zero.
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
19 1
9
Figure 4-1.
Startup Procedure
The important parameters, which have to be chosen for the startup procedure are:
20
Startup speed: it is the speed reached during the startup phase. In the implementation, it coincides
with the “minimum speed”, which is a parameter that can be modified by the user. It should be high
enough to allow a good behavior of the phase estimation process.
Startup time: it is the time required to reach the start up speed. It should be long enough to allow
the estimation algorithm to stabilize (to recover from the initial condition errors). One second is
usually a good value.
Startup current: it is the current level imposed during the startup. It should be kept as low as
possible, depending on the load.
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
2
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
0
5
ATMEL EVALUATION BOARD/KIT IMPORTANT NOTICE AND
DISCLAIMER
This evaluation board/kit is intended for user's internal development and evaluation purposes only. It is
not a finished product and may not comply with technical or legal requirements that are applicable to
finished products, including, without limitation, directives or regulations relating to electromagnetic
compatibility, recycling (WEEE), FCC, CE or UL. Atmel is providing this evaluation board/kit “AS IS”
without any warranties or indemnities. The user assumes all responsibility and liability for handling and
use of the evaluation board/kit including, without limitation, the responsibility to take any and all
appropriate precautions with regard to electrostatic discharge and other technical issues. User indemnifies
Atmel from any claim arising from user's handling or use of this evaluation board/kit. Except for the limited
purpose of internal development and evaluation as specified above, no license, express or implied, by
estoppel or otherwise, to any Atmel intellectual property right is granted hereunder. ATMEL SHALL NOT
BE LIABLE FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMGES RELATING
TO USE OF THIS EVALUATION BOARD/KIT.
ATMEL CORPORATION
1600 Technology Drive
San Jose, CA 95110
USA
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
21 2
1
6
22
Revision History
Doc Rev.
Date
42711A
04/2016
Comments
Initial document release.
Firmware
User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
2
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
2
Atmel Corporation
1600 Technology Drive, San Jose, CA 95110 USA
T: (+1)(408) 441.0311
F: (+1)(408) 436.4200
│
www.atmel.com
© 2016 Atmel Corporation. / Rev.: Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016.
Atmel®, Atmel logo and combinations thereof, Enabling Unlimited Possibilities®, and others are registered trademarks or trademarks of Atmel Corporation in U.S. and
other countries. ARM®, ARM Connected® logo, and others are the registered trademarks or trademarks of ARM Ltd. Other terms and product names may be
trademarks of others.
DISCLAIMER: The information in this document is provided in connection with Atmel products. No license, express or implied, by estoppel or ot herwise, to any intellectual property right
is granted by this document or in connection with the sale of Atmel products. EXCEPT AS SET FORTH IN THE ATMEL TERMS AND CONDITIONS OF SALES LOCATED ON THE
ATMEL WEBSITE, ATMEL ASSUMES NO LIABILITY WHATSOEVER AND DISCLAIMS ANY EXPRESS, IMPLIED OR STATUTORY WARRANTY RELATING TO ITS PRODUCTS
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT
SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE, SPECIAL OR INCIDENTAL DAMAGES (INCLUDING, WITHOUT LI MITATION, DAMAGES
FOR LOSS AND PROFITS, BUSINESS INTERRUPTION, OR LOSS OF INFORMATION) ARISING OUT OF THE USE OR INABILITY TO USE THIS DOCUMENT, EVEN IF ATMEL
HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. Atmel makes no representations or warranties with respect to the accurac y or completeness of the contents of this
document and reserves the right to make changes to specifications and products descriptions at any time without notice. Atmel does not make any commitment to update the information
contained herein. Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications. Atmel products are not inten ded,
authorized, or warranted for use as components in applications intended to support or sustain life.
SAFETY-CRITICAL, MILITARY, AND AUTOMOTIVE APPLICATIONS DISCLAIMER: Atmel products are not designed for and will not be used in connection with any appli cations where
the failure of such products would reasonably be expected to result in significant personal injury or death (“Safety -Critical Applications”) without an Atmel officer's specific written consent.
Safety-Critical Applications include, without limitation, life support devices and systems, equipment or systems for the operation o f nuclear facilities and weapons systems. Atmel
products are not designed nor intended for use in military or aerospace applications or environments unless specifically desi gnated by Atmel as military-grade. Atmel products are not
designed nor intended for use in automotive applications unless
specifi cally designated by Atmel as automotive-grade.
Atmel-42711A-Firmware-User-Guide-Low-Voltage-BLDC-Motor-Control-using-SAM-Devices_UserGuide_042016
Firmware User Guide: Low Voltage BLDC Motor Control using SAM Devices [USER GUIDE]
23 2
3