Copyright © Shimmer Research 2013
Realtime Technologies Ltd
IMU User Manual
All rights reserved
Rev 1.1
1
IMU User Guide
Revision 1.4
Page 1: ...Copyright Shimmer Research 2013 Realtime Technologies Ltd IMU User Manual All rights reserved Rev 1 1 1 IMU User Guide Revision 1 4...
Page 2: ...te products derived from this document without specific prior written permission THIS DOCUMENT IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDI...
Page 3: ...l 16 4 2 Kinematic Parameters 17 4 3 Coordinate Systems 18 5 Applications of IMUs 19 5 1 Gait analysis 19 5 2 Displacement estimation 19 5 3 Orientation estimation 19 5 4 Fall detection 20 6 Practical...
Page 4: ...aughterboard has a rate gyroscope which measures angular velocity The Shimmer 9DoF IMU daughterboard has a both a gyroscope to measure angular velocity and a magnetometer to measure magnetic field whi...
Page 5: ...used to log data or stream data over Bluetooth while SD Log v0 12 0 or greater can be used to log data to the SD card both are available for download from www shimmersensing com For Shimmer 2r BtStrea...
Page 6: ...es acting on it These forces give rise to inertial acceleration This acceleration is defined as the rate of change of velocity of the body in motion It is measured in units of m s2 Acceleration due to...
Page 7: ...ghtless it is suspended in the middle of the hollow cube and not affected by gravity In Figure 3 1 the accelerometer has no forces acting on it i e no inertial acceleration due to movement and no grav...
Page 8: ...celerometer is motionless the ball will rest on the bottom face of the hollow cube Just as you have seen that positive acceleration in the Y axis was detected by the ball pressing against the opposite...
Page 9: ...positive Z direction Measuring 3D Acceleration The Shimmer3 is equipped with tri axial accelerometers as is the Shimmer2r The default representation of its reference axes as assumed in Shimmer applica...
Page 10: ...meter A uni axial accelerometer measures the sum of the inertial acceleration component and gravitational acceleration component acting along its single measuring axis The left side of Figure 3 5 show...
Page 11: ...ght side of Figure 3 5 the leg segment and hence the uni axial accelerometer has moved and come to rest in the position shown In this case the inertial acceleration is zero Thus gravity is the only ac...
Page 12: ...as described previously note that this angle is defined from the X axis Alternatively can be written as where and are the angles that the axis makes with the inertial acceleration vector and the grav...
Page 13: ...eleration vector can be written as where the same notation that has previously been used for the X and Y axes is followed for the Z axis 3 2 Angular rate gyroscope The angular velocity of a body can b...
Page 14: ...gned parallel with the rotation axis then the measured angular velocity will be equal to If on the other hand the measurement axis is perpendicular to the rotation axis then it will measure an angular...
Page 15: ...on where in the world the compass is At the magnetic equator the angle is zero and the magnetic field does act exactly parallel to the Earth s surface In the Northern hemisphere the North end of the...
Page 16: ...ins unchanged from the uni axial case The component measured by the Y axis is given by where is the same angle that was defined previously and illustrated in Figure 3 8 A bi axial magnetometer can be...
Page 17: ...s equal to zero these quantities can both be estimated by calibrating the sensor2 Tri axial sensor measurement Ideally a tri axial IMU should consist of three mutually orthogonal uni axial sensors i e...
Page 18: ...ce can be described using the following 15 variables Winter 1990 Linear displacement of body s centre of mass and Linear velocity of the body s centre of mass and Linear acceleration of the body s cen...
Page 19: ...the coordinate system of another body which may itself be variable then it is known as a relative system For example imagine that two sensors are attached to a person s arm with one below the elbow a...
Page 20: ...accelerometer observations alone Indeed the problem of estimating displacement is not a trivial one and there is vast literature available on the subject A recently published review of displacement e...
Page 21: ...detecting falls using an accelerometer alone would be to calculate the magnitude of the measured acceleration and compare this to a threshold to detect a large spike due to an impact A recent review...
Page 22: ...g Output 16 bit output3 Please refer to the manufacturer s datasheets for detailed information Gyroscope The output of the gyroscope device on the Shimmer3 is digital The gyroscope on the MPU 9150 chi...
Page 23: ...Low Noise Accelerometer RMS noise m s2 3 51 x 10 3 5 09 x 10 3 8 12 x 10 3 Wide Range Accelerometer RMS noise m s2 18 6 x 10 3 27 5 x 10 3 37 2 x 10 3 Gyroscope RMS noise deg s 0 0322 0 0481 0 0785 M...
Page 24: ...and that you have attached either a 9DoF IMU daughterboard or a Gyro IMU daughterboard to the Shimmer baseboard before you try to stream or log gyroscope data Can I use IMUs to analyse gait IMUs are c...
Page 25: ...Medicine and Biology Society EMBC 2010 Buenos Aires Agentina Greene B R McGrath D O Neill R O Donovan K J Burns A Caulfield B 2010 An adaptive gyroscope based algorithm for temporal gait analysis Medi...
Page 26: ...sing a Position Sensor Inertial Measurement Unit Hybrid System IEEE Transactions on Industrial Electronics 57 5 1787 1798 Yadav N Bleakley C 2011 Two stage Kalman filtering for position estimation usi...
Page 27: ...following capabilities apply to your device 1 3 axis Gyroscope with User Interaction controls 2 3 axis Magnetic Sensor with User Interaction controls 3 3 axis Magnetic Sensor and 3 axis Gyroscope wit...
Page 28: ...the Shimmer2 and Shimmer2r baseboards is analog An MMA7361 device from Freescale is used The following approximate values apply to this device Zero output 1 5 V Full scale range 1 5 g 6 0g o Factory o...
Page 29: ...s devices on the Shimmer 9DoF IMU daughterboard and Shimmer Gyro IMU daughterboard is analog Both boards have a fixed reference output and run off of a secondary LDO for improved power supply noise re...
Page 30: ...utton wired to USER_PB SER0_RTS R24 installed R14 installed R23 not installed Functionality is SW defined eg start stop control in logging FW o Optional setting SW1 is reset power R23 installed R24 no...
Page 31: ...185 0 297 0 480 Magnetometer RMS noise normalised local flux 0 0123 0 0138 0 0139 Table 3 Measured RMS noise for Shimmer2r with SR16 6 daughterboard9 Expansion Connector Pin Out for Shimmer2 and Shim...
Page 32: ...applications use an abstraction to configure Shimmer to sample 3 channels of Gyro data call shimmerAnalogSetup addGyroInputs If the Gyro is installed the three ADC signals from the GyroMux board are a...
Page 33: ...eraction controls The following information is provided as legacy support for these devices Component locations for boards without magnetic sensing If the locations marked U1 and U2 are empty there is...
Page 34: ...are not Magnetometer Specifications Resolution 7 mGa Full Scale Measurement range selectable up to 4 5 Ga measurement range Digital interface supports 5 50 Hz Output Data Rate ODR Power consumption i...
Page 35: ...Signal Gyro Input Mode SEL_A0 0 Aux input Mode SEL_A0 1 ADC6 Y Rotation X Y Gyro Zero voltage VREF ADC1 X Rotation X Y Gyro Temperature Sense ADC2 Z Rotation Z Gyro Zero voltage VREF The temperature...
Page 36: ...left and Shimmer IMU enclosure right 9 4 Errata and Updates The accelerometer RMS noise values quoted in Table 6 2 of v1 0 of this User Guide were erroneously labelled as having units of m s2 when in...
Page 37: ...Copyright Shimmer 2016 Realtime Technologies Ltd IMU User Manual All rights reserved Rev 1 4 36...
