Sensorless FOC Motor Control Library Overview¶

Software Overview¶

Sensorless Field-Oriented Control (FOC) Library is made of three main layers: Application layer, HAL Layer, and MSPM0 DriverLib.

1. Application Layer¶

Application Layer is a software layer that does specific functions like Motor control. If any application perform any hardware specific actions, it is done through the HAL Layer APIs.

FOC Library¶

FOC library is a static library that contains generic motor control algorithms algorithms for 3-phase sensorless FOC motor control.

This Library has the following modules integrated :

Align startup
Slow first cycle startup
IPD startup
ISD startup
Brake
Reverse Drive
Deadtime compensation
PI controllers
Openloop
Closeloop
Estimator
Align brake
MTPA
Field Weakening

FOC library also contains the Motor control state machines.

Motor Control Application¶

Motor control Application takes care of register value conversions from users inputs and feeds to the FOC library.

Application Module¶

appInterface : This folder contains the header files for the Input, Control and Status variables.

User can add their custom Input / Ctrl configurations to “appUserInputRegsConfig” API which is periodically called by the application every 200mS when the motor is in not spinning.

ConfigTables All the register map tuning configurations for a given index is defined in the Config tables.

User can add custom values to these tables based on the application use case

Main Application¶

Main application contains the user code which initializes the application modules and periodically calls the configuration updates in While(1) loop.

main.h Configurations¶

User Can define the Default System Configurations from the main.h

Base Address : The default RAM address space for the Input,Ctrl & Status register map structures are defined in main.h. It is recommended to not alter the address space as these will be used by the GUI application for variable referencing.

Hardware Configurations

Gate Driver Selection - Select the connected HW using #ifdef Macro with the available Gate Driver Configurations. Ex: DRV8329/DRV8323/DRV8316/CUSTOM

If user selects a Custom gate driver , It is recommended to choose any of the Gate driver configurations as a starting point and update the SYSCONFIG and HAL based on the pin configurations. The DRV8316/DRV8323 has SPI based Gate Driver Communication with Three Shunt Configuration & DRV8329 Example is based on Single Shunt configuration without SPI communication.

Current Shunt Configuration - User can choose the Current shunt configurations based on the actual number of Shunt Resistors used for Current Sensing.

“#define CURRENT_SHUNT_CONFIG” Macro will be used for the definition of given shunt configuration

Below #ifdef Macro’s can be used to select various current shunt configurations available in the FW.

__CURRENT_THREE_SHUNT_DYNAMIC - For three shunt configuration with dynamic selection of any two shunts based on the Sector
__CURRENT_THREE_SHUNT_XY_Z - For three shunt configuration with Fixed current sensing where XY phases are used for simultaneous sampling and Z phase used for lateral sample.
__CURRENT_TWO_SHUNT_X_Y - For Dual Shunt configurations with X & Y as the respective phases of the three phases used for current sensing
__CURRENT_SINGLE_SHUNT - For Single Shunt current sense Configuration.

For Single shunt configuration user can select _NONINVERT_ISEN or _INVERT_ISEN based on the amplifier input configuration.

For Inverted Isense Configuration - The Voltage across the amplifier decreases as the Current increases.

FULL_SCALE_CURRENT_BASE - Set the Maximum measurable current based on the Current Shunt Amplifier Gain and the Current Sense Resistor.

DC_VOLTAGE_BASE - Set the Maximum measurable phase Voltage based on the Scaled down voltage fed to ADC from the Voltage Divider Circuit.

2. HAL Layer¶

The Hardware Abstraction Layer (HAL) creates an abstraction layer that provides APIs to configure different pins and peripherals. The goal of using HAL is to abstract all device specific configurations which simplifies porting of the library to various hardware by minimizing the updates needed to other components. The HAL is meant to abstract only the required pins or peripherals required for the application while still having flexibility and scalability for porting to other MSPM0 MCUs or motor drivers.

HAL uses the defines generated from TI SysConfig, so it is very easy to change the pin in the TI SysConfig GUI. The HAL automatically follows this without the user having to change any code in the HAL layer.

For Example below is the define for direction pin PORT it is referred by HAL Layer through FOC_GPIO_IN_PORT, this define is mapped to the port number by the TI SysConfig. Thus by changing the PORT in TI SysConfig GUI the direction pin PORT number can be controlled.

/*! @brief GPIO port for direction pin */
#define FOC_GPIO_DIR_PORT           (FOC_GPIO_IN_PORT)

Gate Driver Interface Library¶

Gate Driver Interface Library provides the APIs for reading the currents and voltage channels. Also if the DRV is used it configured the CSA gain and other gate driver register configurations.

The gate driver Interface has 3 parts:

Gate driver Library

Has the APIs to configure the gate driver registers through SPI if the gate driver is a SPI based.

Gate driver peripheral peripheral defines

The Gate driver peripheral defines are in gateDriver.h. Here the ADC memory indexes used for reading the current and voltages are defined.

In the above image we can see that phase U voltage is mapped to ADC channel 6 and the U phase voltage memory index is ADC1_ADCMEM_0, ie A1.6/PB19 is the pin used for U phase voltage, this pin has to be connected to the gate drivers U phase voltage pin. Please refer to the Hardware Guide to know how to connect the Gate driver to the launchpad to make the pin connections.

Gate driver HAL Interface

Gate driver HAL Interface handles the configurations of ADC channels to convert phase voltage inputs and phase current inputs from gate driver.

Single Shunt Configurations:

In single shunt based current sensing, the PWM’s are dynamically shifted near the sector cross overs where there is no margin for current sampling in the non overlapping regions. For this reason, the PWM’s are not center aligned and we assign Compare B indexes of Timer A to achieve this shifting. It is important for user to configure the Compare B index for the PWM’s based on the Pin configuration.

In the above example for DRV8329 ,The primary compare events are selected based on HS PWM pins and the corresponding Timer Compare ports. The secondary Compare events are selected from the remaining Compare indexes from 0-5.

Enabling simultaneous current sampling :¶

Simultaneous current sampling helps to sample the current signals at the same time. This feature helps to improve the performance of FOC by improving the rotor position estimations.

In MSPM0 to enable simultaneous current sampling we need to use both ADCs 0 and 1 and trigger both at the same time. For implementing Simultaneous sampling we need to have any one phase current input connected to both ADC 0 and ADC 1, this additional connection is the minimum requirement needed so that we can sample all the dual current sensing configurations.

The simultaneous current sampling is implemented in DRV8316 gate driver library, refer to drv8316_focHalInterface.c for the implementation code. In DRV8316 gate driver library phase B current is routed for both the ADC 0 & 1 channels to achieve simultaneous sampling in all the dual current sensing configurations : AB, BC, CA (ie, in AB, A is sampled by ADC 0 and B by ADC 1. In BC ,B is sampled by ADC 0 and C by ADC 1).

Controller Interface Library¶

Controller Interface Library provides HAL APIs for controlling the peripherals like timer, gpio etc. The Controller Interface Library uses the gate driver Interface library to set the correct phase and voltage channel configurations to the ADC.

Fig. 5 Peripheral defines in focPeripheralInit.h¶

Important Peripherals and configurations used in FOC¶

1. GPIOs¶

Following are the GPIO’s used by the Application code:

Brake input:

Pin input for applying brake

Direction pin

Pin input for selecting direction

Nfault

Output pin, set low if any fault is detected

nSleep

Output pin, sets the gate driver sleep input

User can change the GPIO pin selection in the TI SysConfig to select any desired pin as shown below.

2. SPI¶

SPI is configured in Sysconfig for gate drivers having SPI interface. The SPI configurations used are given below

SPI	Description
Bit rate	5Mhz
Word size	16 bits
Bit Order	MSB First
Chip select	Active low
Frame Format	4 wire
mode	Controller
Clock polarity	Low
Clock Phase	Data on Second clock edge

User can user the same SPI connection to interface any other device, but need to see if the gate driver spi transmission is busy. Also user need to take care of using a different chip select line.

3. PWM¶

Three PWM channels with complementary outputs are used to drive the motor and one channel is used to trigger the ADC to convert the voltages and currents. TIMER A0 is reserved for generating the PWMs for FOC motor control and user should not use this timer.

TIMER A0 triggers the ADC using event channels, the event channels used are specified in focPeripheralInit.h, user should not use the same event channel used by the Library.

4. ADC¶

The ADC configurations used are given below:

ADC	Description
Conversion Mode	Sequence sampling
Trigger Source	Event triggered
Sample timer	Sample timer 0
Chip select	Active low
Hardware averaging	8 conversions

ADC hardware averaging is used to remove any noise in the signal

ADC is used in converting DC bus voltage, three phase currents and three phase voltages. The gate driver library defines the ADC channel used for conversion and the memory index of the ADC used. Memory indexes used for current and voltages are listed in gateDriver.h. ADC Interrupt occurs after all currents or voltages are sampled.

If user wishes to use ADC to convert any new channels the user should add new memory index by incrementing the Sequence End address in the TI SysConfig and modify the Trigger mode of the new index to “Valid trigger ..” as shown in the below images. Also note to change the Trigger mode of the default Sequence End address to “Trigger will automatically ..” while adding a new sequence end address. The user should not change the ADC interrupt used by FOC, user can enable a new ADC interrupt for their use case.

For phase voltage and phase current configuration the Library sets the channel using the channel listed in gateDriver.h. For DC bus voltage conversion the pin is specified by TI SysConfig and user needs to take care to update the defines in gateDriver.h, if the pin is changed in TI SysConfig.

The first Two memory indexes of the ADC 0 & 1 are used for the Current Sampling / Voltage sampling and shound’t be modified. The DC bus Voltage is sampled from the 2nd Memory Index and user can choose to use any other Memory Index apart from 0 & 1 of ADC 0 & ADC 1 for any custom ADC addition.

5. DAC¶

The DAC configurations used are given below:

DAC	Description
Sample Time Generator Rate	100kSPS
Output Resolution	12 bit
Positive Voltage Reference	VDDA
Negative Voltage Reference	VSSA

DAC is used for real time output of the algorithm variables.

NOTE: While enabling the DAC in TI SysConfig user needs to make sure the DAC output pin is not used

Communication Interface Library¶

Communication Interface Library helps to access the memory of the device using communication peripherals like UART, I2C etc. User can Read or write to the Sensorless FOC registers through the communication peripheral to control the motor externally.

In the current library the UART communication is implementation. Please refer to UART Communication User Guide for more details on communication protocol.

For enabling UART communication with an external device use the below pinouts:

For DRV8316

UART comm pin	LP-MSPM0G3507
UART TX	PA26
UART RX	PA13

For DRV8323RS

UART comm pin	LP-MSPM0G3507
UART TX	PB12
UART RX	PA13

For DRV8329

UART comm pin	LP-MSPM0G3507
UART TX	PB12
UART RX	PA13

3. MSPM0 DriverLib Overview¶

MSPM0 DriverLib is a set of fully functional APIs used to configure, control, and manipulate the hardware peripherals of the MSPM0 platform. Please refer to the DriverLib documentation for more information.