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units [2018/10/12 13:12]
jfduval [Encoders]
units [2019/03/25 12:06] (current)
flabelle
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-====== ​UnitsReferences ​& Conversion Formulas ======+====== ​DataUnits & Conversion Formulas ======
  
-===== IMU =====+===== Data available ​===== 
 + 
 +^Variable ^Full name ^Units ^Notes ^ 
 +|Timestamp | Reception time| ms |Not filtered| 
 +|State_time | Internal time| ms |Not filtered| 
 +|Accelx, y, z | Accelerometer,​ 3 channels| bits | Conversion factor of 8192 LSB/g, not filtered| 
 +|Gyroz, y, z | Gyroscope, 3 channels| bits | Conversion factor of 32.8 LSB/DPS (DPS = degrees per second), not filtered| 
 +|Mot_ang | Motor Angle| ticks | Not filtered| 
 +|Mot_vel | Motor Velocity | ticks/ms | See note 1 | 
 +|Mot_acc | Motor Acceleration | %%rad/s^2%% | See note 1 | 
 +|Mot_curr | Motor Current | mA | Not filtered | 
 +|Mot_volt | Motor Voltage | mV | Not filtered| 
 +|Batt_volt | Battery Voltage | mV | Analog: 1st order RC, fc = 3.56kHz. Digital: moving average of 32 samples, equivalent to 138Hz.| 
 +|Batt_curr | Battery Current | mA | Analog filter, 884Hz| 
 +|Temp | Temperature | °C | Sampled at 10kHz, moving average of 16 (equivalent to 277Hz)| 
 +|Genvar_3 | Generic Variable #3 (currently used for torque at the ankle)| 10*N.m | Not filtered | 
 +|Ank_ang | Ankle Angle | degrees x 10 | Not filtered | 
 +|Ank_vel | Ankle Velocity | 10 degrees/sec | Filtered 3rd order Butteworth with 30 Hz cutoff | 
 +|Ank_from_mot | - | - | Internal variable| 
 +|Cur_stpt | - | - | Internal variable| 
 +|Step_energy |Step Energy | J x 10| Integrated positive power, not filtered | 
 +|Walking_state | - | - | Internal variable| 
 +|Gait_state | - | - | Internal variable| 
 +//**Note 1:** Mot_vel and Mot_acc use custom C filters optimized for speed. We suggest calculating motor velocity and motor acceleration in post-processing if you need them and would like to avoid lag.// 
 + 
 +===== Additional information ===== 
 +==== IMU ====
  
 Two references are used: [[https://​www.invensense.com/​products/​motion-tracking/​6-axis/​mpu-6500/​|MPU-6500]] and [[https://​www.invensense.com/​products/​motion-tracking/​9-axis/​mpu-9250/​|MPU-9250]]. Their scales and gains are the same. The MPU-9150 includes a magnetometer,​ not currently used (on FlexSEA-Rigid it's mounted on the motor... so it's just a bad position sensor). Two references are used: [[https://​www.invensense.com/​products/​motion-tracking/​6-axis/​mpu-6500/​|MPU-6500]] and [[https://​www.invensense.com/​products/​motion-tracking/​9-axis/​mpu-9250/​|MPU-9250]]. Their scales and gains are the same. The MPU-9150 includes a magnetometer,​ not currently used (on FlexSEA-Rigid it's mounted on the motor... so it's just a bad position sensor).
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 Accelerometer range can be ±2g, ±4g, ±8g or ±16g. Our systems typically come with ±4g. The associated gain is 8192 LSB/g. Accelerometer range can be ±2g, ±4g, ±8g or ±16g. Our systems typically come with ±4g. The associated gain is 8192 LSB/g.
  
-===== Voltages & Currents ​=====+==== Voltages & Currents ====
  
 Currents are reported in mA, and voltages in mV. In some occasions the stack will bit-shift them to compress the values in a byte or two instead of 4. Currents are reported in mA, and voltages in mV. In some occasions the stack will bit-shift them to compress the values in a byte or two instead of 4.
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 Motor variables are signed. Bus voltages are unsigned. Motor variables are signed. Bus voltages are unsigned.
  
-===== Encoders ​=====+==== Encoders ====
  
 Motor and joint encoder angles are reported in ticks. 1 tick is 1 LSB for a given encoder. As an example, the [[http://​ams.com/​eng/​Products/​Magnetic-Position-Sensors/​Angle-Position-On-Axis/​AS5047P|AS5047P absolute magnetic position sensor]] is used for motor commutation on most FlexSEA systems. It has a 14-bit resolution; 16384 ticks/​rotation. One tick is equivalent to 360/​2^14=0.02197 degrees. Motor and joint encoder angles are reported in ticks. 1 tick is 1 LSB for a given encoder. As an example, the [[http://​ams.com/​eng/​Products/​Magnetic-Position-Sensors/​Angle-Position-On-Axis/​AS5047P|AS5047P absolute magnetic position sensor]] is used for motor commutation on most FlexSEA systems. It has a 14-bit resolution; 16384 ticks/​rotation. One tick is equivalent to 360/​2^14=0.02197 degrees.
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 For integrated systems different units can be used (ex.: 10*degrees). Please refer to the system'​s page, or contact us. For integrated systems different units can be used (ex.: 10*degrees). Please refer to the system'​s page, or contact us.
-===== Other =====+==== Other ====
  
 Temperatures are reported in Celsius. Temperatures are reported in Celsius.
units.1539349923.txt.gz · Last modified: 2018/10/12 13:12 by jfduval