ME405_FP_ABFilter.ABFilter Class Reference

A class implementation of an alpha beta filter for position and velocity estimation. More...

Public Member Functions
def	__init__ (self, alpha=0.85, beta=0.005, prescaler=10 **6, x_not=0, v_not=0, t_not=0, useUtime=True)
	A method to initialize an ABFilter. More...
def	update (self, x_new, t_new)
	Used to update estimate a new velocity and position based on a measured position and time. More...
def	setAB (self, alpha=None, beta=None)
	A method to change the alpha and beta values used for position and velocity estimation. More...
def	setState (self, x=None, v=None, t=None)
	A method to reset the ABFilter to a specified position, velocity, and time. More...

Public Attributes
	alpha
	The alpha value used for velocity estimation.
	beta
	The beta value used for velocity estimation.
	x
	The most recent filtered x position.
	v
	The most recent filtered y position.
	t
	The most recent time tick, typically in microseconds.
	useUtime
	wether or not time ticks are generated with utime
	prescaler
	The prescaler to multiply the velocity by to get x units per second.

Detailed Description

A class implementation of an alpha beta filter for position and velocity estimation.

Alpha beta filters are usefull for more acuratley estimating position and velocity from granular readings, such as a slow spinning encoder or a one pole hall efect rpm sensor.

Author

Eliot Briefer

Constructor & Destructor Documentation

__init__()

def ME405_FP_ABFilter.ABFilter.__init__	(		self,
			alpha = 0.85,
			beta = 0.005,
			prescaler = 10**6,
			x_not = 0,
			v_not = 0,
			t_not = 0,
			useUtime = True
	)

A method to initialize an ABFilter.

Parameters

alpha	The alpha value
beta	The beta value
prescaler	Used to correct velocity into units/sec. Prescaler value is
x_not	Initial position
v_not	Initial velocity
t_not	Initial tick (typically in micro seconds)
useUtime	Wether or not to use utime.ticks_diff(). Set to false if time ticks arent generated using utime.ticks_ms() or utime.ticks_us().

Member Function Documentation

setAB()

def ME405_FP_ABFilter.ABFilter.setAB	(		self,
			alpha = None,
			beta = None
	)

A method to change the alpha and beta values used for position and velocity estimation.

Parameters

alpha	The new alpha value, should be < 1.
beta	The new beta value, should be small, typically < 0.1

setState()

def ME405_FP_ABFilter.ABFilter.setState	(		self,
			x = None,
			v = None,
			t = None
	)

A method to reset the ABFilter to a specified position, velocity, and time.

Parameters

x	The set position.
v	The set velocity.
t	The set time tick.

update()

def ME405_FP_ABFilter.ABFilter.update	(		self,
			x_new,
			t_new
	)

Used to update estimate a new velocity and position based on a measured position and time.

Parameters

x_new	new x reading
t_new	new t tick, typically in us from utime.ticks_us()

Returns

A tuple of (estimated position, estimated velocity)

---

The documentation for this class was generated from the following file:

• ME405_FP_ABFilter.py