Wiimotes and Robots David Lippman Pierce College Ft Steilacoom.
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Transcript of Wiimotes and Robots David Lippman Pierce College Ft Steilacoom.
Wiimotes and Robots
David Lippman
Pierce College Ft Steilacoom
“Real World” What do we mean by this? Capturing data for analysis is cool, but Can we solve a problem, and see it in action?
Wiimotes Can connect over Bluetooth to computer 3-axis accelerometer Infrared camera with blob detection (4 pts)
Interacting with the Wiimote
Low LevelWiiuse / WiiuseJ (C / Java)Wiimotelib (C#)
High LevelGlovePIE
Problem #1
Prereq: AlgebraProblem: Wiimote returns dot values in the range x: 0-1023, y: 0-767 GlovePIE maps mouse position to a 0-1 scale in
the x and y How do we map Wiimote position to a mouse
position?
Prob #1 Soln
Wiimote pointing left puts dots on the right, so need to invert x. Don’t need to invert y since Mouse.y measures down from the top of the screen
Mouse.x = 1 - wiimote.dot1x/1023 Mouse.y = wiimote.dot1y/767
Problem #2
Prereq: TrigProblem: Wiimote returns dot values in the range x: 0-1023, y: 0-767, roll GlovePIE maps mouse position to a 0-1 scale in
the x and y How do we map Wiimote position to a mouse
position, compensating for roll?
Prob #2 Soln
Angle = asin(Wiimote.gx/1) or use atan2 Angle is off horiz Find xcamera, ycamera
Convert to polar Adjust for roll angle Convert back to Cartesian,
map to mouse
Problem #3
Prereq: Algebra
Problem:
How do we determine 3D position of Wiimote in space? (using triangles)
(Assume no roll for simplicity)
Prob #3 SolnCalculate distance between dots
Distance from camera = 264/dot dist
Dist at 1m = 0.1mreal / 132 pxcamera
X position:
1 m
200 px = 200*0.1/132 = 0.1515 m
4 m
0.1515 0.606
1 4
m m
m m
Problem #4
Prereq: TrigProblem: How do we determine 3D position of Wiimote in
space? (using trig) (Assume no roll for simplicity)
Could we have done this with 2 Wiimotes and one dot?
Prob #4 Soln Camera FOV = about 45 degrees Pixels/degree = 1024/45 = 22.8
200px → 8.8 deg1 m
4 m
4sin(8.8 ) 0.611x m
0.1dist
1dot separation
2tan22.8 pixels/degree
m
How different?Distance determination:
Dis
t (m
)
Dot separation (pixels)
Relative difference
X-location determination:
Pixel x
actual x
Relative difference
Johnny Lee's Youtube Video
Problem #5Prereq: Linear Algebra
Problem:
Mark 4 points on a projected plane (projector image) that correspond to 4 points of a unit square (screen coordinates). Find the transformation that maps points on the projected plane to the unit square.
u
v
x
y
Prob #5 SolnHomogenous Coordinates: , ,x y w
xx wyy w
u
v
x
y
, , , ,1
1
a d g
x y w u v b e h
c f
1
1
au bv cx
gu hv
du ev fy
gu hv
1
1
au bv cx
gu hv
du ev fy
gu hv
x au bv c xgu xhv
y du ev f ygu yhv
0 0 0 0 0 0
1 1 1 1 1 1
2 2 2 2 2 2
3 3 3 3 3 3
0 0 0 0 0 0
1 1 1 1 1 1
2 2 2 2 2 2
3 3 3 3 3 3
1 0 0 0
1 0 0 0
1 0 0 0
1 0 0 0
0 0 0 1
0 0 0 1
0 0 0 1
0 0 0 1
u v u x v x a
u v u x v x b
u v u x v x c
u v u x v x d
u v u x v x e
u v u x v x f
u v u x v x g
u v u x v x h
0
1
2
3
0
1
2
3
x
x
x
x
y
y
y
y
Using 4 corner points, this gives:
Reduces further using unit square for (u,v)
Solve using Gaussian Elimination.
To map back to (u,v), find inverse of the mapping matrix.
Problem #6
Prereq: Integral Calculus / DiffEq Problem:
Use the accelerometer readings to estimate distance the Wiimote moves.
Prob #6 Soln
Simplistic approach:s0 = 0, v0 = 0. Step: Δt = .05 secLoop: vn = vn-1 + .05a sn = sn-1 + .05vn
However, accelerometers are very noisy, so this is not very accurate. In fact, it’s so horrible I’m not even going to show it!
Arduino
Computer on a chip 14 digital I/O, w/ 6
pseudo analog out 6 analog inputs 16KB storage 1KB RAM Serial over USB Open hardware Open software
Problem #7
Prereq: Algebra
Problem: Create a car backup alarm using distance sensor and LED light.
Distance sensor can detect time (in microseconds) that a sound takes to echo back.
Prob #7 Soln
dist = rate*timerate = experimentally determined, or speed
of sound converted to appropriate unitsblink delay proportional to distance
Does direct proportionality look good? Should it be quadratic? Logarithmic?
Problem #8
Prereq: Algebra
Problem: Map Nunchuck joystick data (values -105 to 105) to PWM values (500 to 2500) for the Servos
Prob #8 Soln
Joystick Servo
-105 2500
-105 500
500 2500 200
105 ( 105) 21
200Servo (Joystick 105) 2500
21
m
Problem #9
Prereq: Trig
Problem: Use the Pan/Tilt laser pointer to draw a circle
Prob #9 Soln
Use parametric equations:t=0Loop: x = cos(t) y = sin(t) map (x, y) to Servos t = t + .1 delay(20)
Problem #10
Prereq: Pre-algebraProblem: In a robot with differential drive,
each wheel can turn at a different rate. If the wheels are 10cm apart and the outside wheel turns at full speed, at what fraction of full speed will the inside wheel need to turn to drive a circle with inner radius 50cm?
Prob #10 Soln
10cm 50cm
Cinside = 2π(50) cm
Coutside = 2π(50+10) cm
Speedinside = (2π(50) cm)/unit time
Speedoutside = (2π(50+10) cm)/unit time
Ratio of speeds = 50 / (50 + 10) = 5/6
Problem #11
Prereq: Trig
Problem: Ballistics trajectories. Experimentally determine initial velocity, then adjust launch angle to hit a target.
Have a class competition to see who can come closest!
Prob #11 Soln0
20 0
0
0 0
0 00 0
00
To determine :
4.9
assuming 0
sin( )
4.9horizontal hit dist
sin( )cos( )
4.9
9.8
sin(2 )
v
hit
v
s t v t s
s
vt
d
vd v
dv
0
0
00
20
12
0
To find launch angle:
again assuming 0
sin( )
4.9to achieve horizontal hit dist
sin( )cos( )
4.9
sin(2 )
9.8
1 9.8sin
2
hit
s
vt
d
vd v
vd
d
v
Advanced ideas
Kalman filters Gesture recognition (hidden Markov
model) Augmented Reality
Playtime
Wii Quizzer Wii Buzzer
Correlation doesn't imply causation, but it does waggle its eyebrows suggestively and gesture furtively while mouthing 'look over there'.