Your Knock Is My Command: Binary Hand Gesture Recognition on Smartphone with Accelerometer

Algorithm 1

The pseudocode of bit cutting process.

	Input: α, the coefficients of the low-pass filter
	β, the coefficients to adjust the fluctuation characteristic
	Emax, the user-set maximum cumulative error threshold
	Ebavg, the average error of the initial quiet period
	Output: A complete gesture signal segment
	/^∗ initialization ^∗/;
	i ← 0, A ← [];
	k ← 0, Segment ← [], P ← [];
	while Get ith 3-axis acceleration sample: Ax, Ay, Az do
	/^∗ signal synthesis and filtering ^∗/;
	;
	;
	;
	/^∗ SW or SWAB ^∗/;
	start ← Segment[k − 1], end ← i − 1;
	← linear regression to fit a line for A[start: end];
	for j = start ⟶ end do
	Ecum ← Ecum +
	end
	if Ecum > Emaxthen
	/^∗ a new segment is cut out by SW or SWAB ^∗/;
	Segment[k] ← i − 1;
	Eavg ← 1/ai Ecum;
	/^∗ set the fluctuation characteristic ^∗/;
	if Eavg < βEbavgthen
	P[k] ← 0;
	else
	P[k] ← 1;
	end
	/^∗ process by merge Algorithm ^∗/;
	Segment, P, k ← merge(Segment, P, k);
	/^∗ check if a complete segment is cut-out ^∗/;
	if [P [0], P [1], P [2]] = [1, 0, 1] then
	TS ← A[0: Segment[0]];
	output TS for recognition;
	end
	k ← k + 1;
	end
	end