Typical Motion Table Test Data

Typical Angle Measurement Data 270° CW Rotation Followed by 270° CCW Rotation Model F20

The SPI Data Bus  output "angle  "  was collected during a motion table test and the displacement angle is shown in the figure to the left.  The test sequence comprised  a Bias Compensation Command, followed by the motion table rotation by 270° clockwise motion, and then by 270° of counter clockwise motion coming back to the original position.  Angular rate during the clockwise rotation consisted of a ramp up to constant 22 °/sec then a ramp down to 0 °/sec. .  The operation was then reversed for the 270° counter clockwise motion.  Angle accuracy at the peak angle of 270° is 0.3% of full scale.  The Angle value at the start is .09° and 0.53° at the end of the motion.

Integrated Angle Values from Raw Bias & Compensated Bias Data Model F20 Data Three Bias Compensation Techniques 1-Bias Compensation, 2- Home/Zero Reference, & 3- Combined Bias Compensation & Home/Zero Reference

	Figure 1a- . Zero Reference Compensation vs. Uncompensated Bias Zero Reference is detected and Angle accumulator is reset to: 0º	Figure 1b- Expanded View  Zero Reference Compensation vs. Uncompensated Bias While Zero Reference is active, the Angle value is held to 0° until angular motion commences which in this case is at 3.3 seconds.
	Figure 1c   Bias Compensation vs. Uncompensated  Bias Bias compensation is applied prior to the start of the motion.  Angle value at the start (1.7 sec.) is 0.3125° and 0.8125° at the end (44.8 sec.) of motion .	Figure 1d Expanded View Bias Compensation vs. Uncompensated  The Angle difference at the end of motion is 11° for the uncompensated angle.
	Figure 1e  Bias & Zero Reference Compensation vs.  Uncompensated  Bias When Zero Reference can be employed along with Bias compensation superior performance can be achieved.  The Angle value at peak 1 is 44.64° and at peak 2 is 44.46°.  The 1st negative Angle value is -44.68° and the 2nd negative peak is - 44.75°.	Figure 1f   Expanded View of Angle @ 0° Crossover Bias & Zero Reference Compensation vs. Uncompensated

Model F15  Bias Compensation Stability vs. Time

Accumulated Compensated Bias vs.  Time (sec.)

Gyro bias varies with time, as such the bias sample and related spec is valid for a limited time. The above chart is the Angle value under the following conditions: Bias Compensation set at the start of the data collection Ambient temperature relatively constant No motion Time on the graph is in seconds Time Variation Mitigation.  To minimize the effect of bias change with time, the Event Stop/Start feature can be employed.  If the motion is completed within 30-60¹ seconds, the Event commend set to '1' value will hold the value to the last angle value.  At a subsequent time when the next angular motion is commanded, initiate a set_bias, command the  Event Start/Stop to a "0' and start the motion ¹ This assumes the desire to maintain the Angle error ( due to bias) over the angular motion  to less than 0.5º - 1.0º

BioMechanics   Tracking Human Body Motion [back]

Calculating the elevation change in foot placement as a subject climbs a staircase from Femur & Tiba Angle Changes

Data Collected with Arrow3i Angle Measurement & Control Module placed on the upper leg (femur) just above the knee and just below the knee on the Tibia.  Sensor attachment is to a elastic knee brace.  Acknolwedgement that the muscle and skin motion effect the measurements but they are within the allowable limits of tracking a human subject.

The first graph below shows the calculated change in elevation vs. time as the subject climbs four stairs.The elevation calculation is derived from the Femur and Tibia angle change from rest along with measurements of the hip joint to knee joint and the knee joint to heel bottom.  The step rise is 7.25 in. and the total elevation from the graph is 28.6 in.   The second graph shows the recorded Femur and Tibia Angles for both the climbing up 5 stairs and the descent to the orginal starting position.

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