advlib-ble-gatt - npm Package Compare versions

Comparing version 1.0.2 to 1.1.0

lib/bluvib.js

@@ -7,2 +7,3 @@ /**
 
+const dsp = require('./dsp');
 const utils = require('./utils');
@@ -22,2 +23,5 @@
 const CHARS_PER_SAMPLE = 4;
+const STANDARD_GRAVITY = 9.80665;
+const ISO_20816_MIN_FILTER_FREQUENCY = 10;
+const ISO_20816_MAX_FILTER_FREQUENCY = 1000;
 
@@ -205,2 +209,14 @@
 
+  // Calculate velocityOverall for each axis: this is computation-intensive and
+  // make take a non-negligible amount of time to execute, especially for long
+  // time series and on resource-constrained computers!
+  let velocityOverall = [];
+  accelerationTimeSeries.forEach((samples) => {
+    velocityOverall.push(calculateAverageVelocityOverall(samples,
+                                                data.accelerationSamplingRate));
+  });
+
+  if(velocityOverall.every((value) => Number.isFinite(value))) {
+    data.velocityOverall = velocityOverall;
+  }
   data.accelerationTimeSeries = accelerationTimeSeries;
@@ -222,4 +238,67 @@ data.acceleration = acceleration;
 
+/**
+ * Calculate the average velocity overall from the given acceleration time
+ * series, dividing it into subsamples.
+ * @param {Array} samples The acceleration time series.
+ * @param {Number} samplingRate The sampling rate of the time series.
+ * @return {Number} The velocity overall.
+ */
+function calculateAverageVelocityOverall(samples, samplingRate) {
+
+  // Remove any DC offset from the time series samples
+  let offsetSamples = dsp.dcOffset(samples);
+
+  // Split the time series samples into up to four sets of at least 256 samples
+  let sampleSets = dsp.createPowerOfTwoLengthSubSamples(offsetSamples, 256, 4);
+
+  // Convert to m/s/s, then calculate and average the velocityOverall subsamples
+  let velocityOverallSum = 0;
+  sampleSets.forEach((sampleSet, index) => {
+    sampleSet.forEach((sample, index) => {
+      sampleSet[index] = sample * STANDARD_GRAVITY; // g to m/s/s
+     });
+    velocityOverallSum += calculateVelocityOverall(sampleSet, samplingRate) ||
+                          NaN; // Void the average should a calculation fail
+  });
+
+  // Take the average of the sets
+  return velocityOverallSum / sampleSets.length;
+}
+
+
+/**
+ * Calculate the velocity overall from the given acceleration time series.
+ * @param {Array} samples The acceleration time series.
+ * @param {Number} samplingRate The sampling rate of the time series.
+ * @return {Number} The velocity overall.
+ */
+function calculateVelocityOverall(samples, samplingRate) {
+
+  // Apply a Hann window to the time series
+  let windowedSamples = dsp.hannWindow(samples);
+
+  // Perform a FFT on the windowed samples
+  let fft = dsp.fft(windowedSamples, samplingRate);
+
+  // Abort should the FFT fail
+  if(fft === null) { return null; }
+
+  // Integrate over frequency (within filter window) to get velocities
+  let filteredVelocities = [];
+  for(let bin = 0; bin < fft.numberOfBins; bin++) {
+    if((fft.frequencies[bin] >= ISO_20816_MIN_FILTER_FREQUENCY) &&
+       (fft.frequencies[bin] <= ISO_20816_MAX_FILTER_FREQUENCY)) {
+      let velocity = fft.magnitudes[bin] / fft.frequencies[bin];
+      filteredVelocities.push(velocity);
+    }
+  }
+
+  // Take the RMS of the velocities divided by the square root of the noise
+  // bandwidth of the Hann window (1.5) to obtain velocity overall
+  return dsp.rms(filteredVelocities) / Math.sqrt(1.5);
+}
+
+
 module.exports.process = process;
 module.exports.combine = combine;
 module.exports.supportedServiceUuids = SUPPORTED_SERVICE_UUIDS;

package.json

@@ -18,3 +18,3 @@ {
   ],
-  "version": "1.0.2",
+  "version": "1.1.0",
   "engines": {
@@ -21,0 +21,0 @@ "node": ">=6.0.0"

No alert changes

Improved metrics

Total package byte prevSize

53016

increased by25.69%

Number of package files

12

increased by9.09%

Lines of code

877

increased by44.01%

No dependency changes