High Performance MEMS IMU

ER-MIMU-M02  High Performance MEMS IMU

Introduction

ER-MIMU-M02 is an inertial measurement unit (IMU) based on micromechanical technology (MEMS), including a built-in MEMS gyroscope with 2°/h (Allan)  bias instability and a MEMS accelerometer with 24μg (Allan) bias instability. It is used to measure the three-axis angular rate and three-axis acceleration of the carrier. Through the communication protocol, the gyroscope and accelerometer data with error compensation (including temperature compensation, installation misalignment Angle compensation, nonlinear compensation, etc.) can be solved to obtain the carrier attitude, velocity, displacement and other information. It also has a built-in three-axis magnetic sensor and air pressure sensor. The magnetometer helps with orientation and can be used to calibrate the data and orient it to the correct position. The product has high reliability and strong environmental adaptability.

Features

Three-axis digital gyroscope:

Dynamic measurement range: ±450º/s;

Bias instability: 2 º/h (Allan variance);

Angular random walk: 0.15º/√h.

Three-axis digital accelerometer:

Dynamic measurement range: 16g;

Bias instability: 24μg (Allan variance);

High reliability: mean time between failures > 20000h;

Ensure accuracy over the full temperature range (-40°C~80°C): Built-in high-performance temperature calibration and compensation algorithm;

Communication interface: 1 SPI, slave mode.

Application

Space-based fields: unmanned aerial vehicles, aerial photography, agricultural plant protection, photoelectric detection stability;

Land-based fields: vehicle navigation, vehicle satellite communications, forest and land monitoring, high-speed railway track inspection;

Sea-based fields: hydrological Measurement, waterway detection, shipboard positioning communication, unmanned surface vehicle.

Specifications

Parameter	Test condition	Min value	Typical value	Max value	Unit
Gyroscope
Measuring range			±450		º/s
Bias instability	Allan variance		2		º/h
Bias stability			6		º/h
Random Walk			0.15		º/√h
Bias Repeatability	1 σ		6		º/h
Bias temperature coefficient			±0.001		dps/℃
Scale factor non-linearity	1 σ		0.01		%FS
Bandwidth(3dB)			96		Hz
Accelerometer
Measuring range			±16		g
Bias instability	Allan variance		24		μg
Bias stability			70		μg
Bias Repeatability	1 σ		150		μg
Bias temperature coefficient			±0.1		mg/℃
Noise density			60		ug/√Hz
Bandwidth(3dB)			83		Hz
Magnetometer
Dynamic measurement range		±2.5			Gauss
Resolution			120		uGauss
Noise Density			50		uGauss
Bandwidth			200		Hz
Barometer
Pressure range		450		1100	mbar
Overall error			6
Resolution			0.1		mbar
Absolute measurement accuracy			1.5		mbar
Long-term stability			±1		mbar/yr
Communication Interface
1 way SPI	Baud rate			15	MHz
Electrical specification
Voltage		3	3.3	3.6	V
Power dissipation				1.5	W
Ripple wave	P-P			100	mV
Structural characteristics
Dimension	47×44×14mm
Weight			50		g
Operating environment
Operating temperature		-40		80	℃
Storage temperature		-45		85	℃
Vibration			3g, 10~2000Hz
Impact			30g, 11ms
Mean time between failures			20000		h
Reliability
Continuous working hours			120		h

 

Dimension

Coordinate system definition

The coordinate systems for the 3 gyroscopes (x g, y g, z g) and 3 accelerometers (x a, y a, z a) are defined as shown in the figure below, with the arrows in a positive direction.

Read and write data

ER-MIMU-M02 is an autonomous sensor system that automatically activates when an active power supply is present. Once the initialization process is complete, it begins sampling, processing, and loading the calibrated sensor data into the output registers, which can be accessed via the SPI port. The SPI port is usually connected to a compatible port of the embedded processor, and the connection diagram is shown in the figure. Four SPI signals support synchronous serial data transmission. In the factory default configuration, the DIO2 pin provides a data-ready signal; When new data is available in the output data registers, the pin goes high.

1 General Purpose Host Processor SPI Settings

Processor settings	introduce
Host mode	ER-MIMU-M02 used as a slave
SCLK ≤ 15 MHz	Maximum serial clock rate
SPI mode 3	CPOL = 1 (polarity)， CPHA = 1 (phase)
MSB Priority mode	Positional order
16-bit mode	Shift register/data length

2 SPI Communication

If the previous command is a read request, the SPI port supports full-duplex communication, and the external processor can write DIN at the same time as reading DOUT, as shown in the following figure.

2.1 SPI read and write timing

Read sensor data

The ER-MIMU-M02 automatically starts and activates page 0 for data register access. After accessing any other page, the 0x00 should be written to the PAGE_ID register (DIN = 0x8000) to activate page 0 in preparation for subsequent data access. A single register read operation requires two 16-bit SPI cycles. In the first cycle, the bit allocation function in Figure 1 is used to request a read of the contents of a register; In the second cycle, the register contents are output via DOUT. The first digit of the DIN command is 0, followed by the high or low address of the register. The last 8 bits are extraneous, but the SPI requires the full 16 SCLKs to receive requests. The following diagram shows two consecutive register reads, first DIN = 0x1A00, requesting the contents of the Z_GYRO_OUT register, and then DIN = 0x1800, requesting the contents of the Z_GYRO_LOW

2.2 Example of an SPI read operation

User Register Memory Mapping

R/W	PAGE_ID	address	default	Register description
R/W	0x00	0x00	0x00	Page identifier
R	0x00	0x0E	N/A	temperature
R	0x00	0x10	N/A	x axis gyroscope output, low word
R	0x00	0x12	N/A	x axis gyroscope output,high word
R	0x00	0x14	N/A	y axis gyroscope output, low word
R	0x00	0x16	N/A	y axis gyroscope output,high word
R	0x00	0x18	N/A	z axis gyroscope output, low word
R	0x00	0x1A	N/A	z axis gyroscope output,high word
R	0x00	0x1C	N/A	x axis accelerometer output, low word
R	0x00	0x1E	N/A	x axis accelerometer output,high word
R	0x00	0x20	N/A	y axis accelerometer output, low word
R	0x00	0x22	N/A	y axis accelerometer output,high word
R	0x00	0x24	N/A	z axis accelerometer output, low word
R	0x00	0x26	N/A	z axis accelerometer output,high word
R	0x00	0x28	N/A	x axis Magnetic output,high word
R	0x00	0x2A	N/A	y axis Magnetic output,high word
R	0x00	0x2C	N/A	z axis Magnetic output,high word
R	0x00	0x2E	N/A	Barometric pressure output，low word
R	0x00	0x30	N/A	Barometric pressure output，high word

2.3 Transform formulas

Current temperature =25+ TEMP_OUT* 0.00565

X axis gyroscope for example	X_GYRO_OUT	X_GYRO_LOW
	1LSB=0.02°/S	The weight of the MSB is 0.01°/s, and the weight of the successors is half that of the previous one
	0.02*X_GYRO_OUT	0.01*MSB+0.005*.......

YZ gyroscopes are calculated in a similar way to X-axis gyroscopes。

X axis accelerometer for example	X_ACCL_OUT	X_ACCL_LOW
	1LSB=0.8mg	The weight of the MSB is 0.4mg, and the weight of the successors is half that of the previous one
	0.8*X_ACCL_OUT	0.4*MSB+0.2*.......

YZ accelerometers are calculated in a similar way to X-axis accelerometers。

X x axis Magnetic	X_MAGN_OUT
	1LSB=0.1mGauss
	0.1*X_MAGN_OUT

YZ axis magnetometers are calculated in a similar way to X-axis magnetometers。

Example of barometric pressure calculation	BAROM_OUT	BAROM_LOW
	1LSB=40ubar	The MSB is weighted at 20ubar, and the successors are weighted half the weight of the previous one
	40*BAROM_OUT	20*MSB+10*.......

Note: For gyroscope, accelerometer, magnetic fraction high 16bit, and low 16bit, the final result of addition is calculated separately

Electrical interfaces

Pin serial number	name	type	description
10,11,12	VDD	power supply
13，14，15	GND	Power Ground
7	DIO1	I/O	Generic I/O, configurable
9	DIO2	I/O
1	DIO3	I/O
2	DIO4	I/O
3	SPI-CLK	input	The SPI defaults to slave mode
4	SPI-MISO	output
5	SPI-MOSI	input
6	SPI-CS	input
8	RST	input	reposition
16~24	NC	spare	Manufacturer reserved

Exterior structure

The product is mounted through 4XΦ2.4 through holes, and 4XM2 screws (plus elastic washers and flat washers) are used for mounting. When the connector is installed, the plug should be connected to the receptacle. The product mating connector is Samtec CLM-112-02-L-D

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