qLTISys

API for the qLTISys library for recursive evaluation of LTI systems defined by transfer functions. More...

Data Structures
struct	qLTISys_t
	A LTI system object. More...

Macros
#define	QLTISYS_DISCRETE
	Macro to specify that the system is time-discrete.

Typedefs
typedef qNumA_state_t	qLTISys_ContinuosX_t
	Type to specify continuos states.
typedef float	qLTISys_DiscreteX_t
	Type to specify continuos states.

Functions
float	qLTISys_Excite (qLTISys_t *const sys, float u)
	Drives the LTI system recursively using the input signal provided.
int	qLTISys_SetDelay (qLTISys_t *const sys, float *const w, const size_t n, const float initVal)
	Set the input delay for LTI system.
int	qLTISys_SetSaturation (qLTISys_t *const sys, const float min, const float max)
	Setup the output saturation for the LTI system.
int	qLTISys_IsInitialized (const qLTISys_t *const sys)
	Check if the LTI system is initialized.
int	qLTISys_SetInitStates (qLTISys_t *const sys, const float *const xi)
	Set the initial states for the given system.
int	qLTISys_Setup (qLTISys_t *const sys, float *num, float *den, void *x, const size_t nb, const size_t na, const float dt)
	Setup and initialize an instance of a LTI system.
float	qLTISys_DiscreteFIRUpdate (float *w, const float *const c, const size_t wsize, const float x)
	Evaluate the discrete FIR filter by updating the delay lines of x inside the window w of size wsize with the coefficients given in c. If c it's not supplied, this function just perform the window update.
int	qLTISys_SetIntegrationMethod (qLTISys_t *const sys, qNumA_IntegrationMethod_t im)
	Set integration method for continuos systems.

Detailed Description

API for the qLTISys library for recursive evaluation of LTI systems defined by transfer functions.

For a brief description of this module, please read Recursive LTI Systems Evaluation by transfer functions.

Function Documentation

qLTISys_DiscreteFIRUpdate()

float qLTISys_DiscreteFIRUpdate	(	float *	w,
		const float *const	c,
		const size_t	wsize,
		const float	x )

Evaluate the discrete FIR filter by updating the delay lines of x inside the window w of size wsize with the coefficients given in c. If c it's not supplied, this function just perform the window update.

Parameters

[in,out]	w	An array of wsize elements that holds the window with the delay lines of x.
[in]	c	An array of wsize elements with the coefficients of the FIR filter. Coefficients should be given in descending powers of the nth-degree polynomial. To ignore pass NULL.
[in]	wsize	The number of elements of w.
[in]	x	A sample of the input signal.

Returns

If c is provided, returns the evaluation of the FIR filter. otherwise return the sum of the updated window w.

qLTISys_Excite()

float qLTISys_Excite	(	qLTISys_t *const	sys,
		float	u )

Drives the LTI system recursively using the input signal provided.

Precondition

Instance must be previously initialized by qLTISys_Setup()

Note

The user must ensure that this function is executed in the time specified in dt either by using a HW or SW timer, a real time task, or a timing service.

Parameters

[in]	sys	A pointer to the LTI system instance
[in]	u	A sample of the input signal that excites the system

Returns

The system response.

qLTISys_IsInitialized()

int qLTISys_IsInitialized

(

const qLTISys_t *const

sys

)

Check if the LTI system is initialized.

Returns

1 if the system has been initialized, otherwise return 0.

qLTISys_SetDelay()

int qLTISys_SetDelay	(	qLTISys_t *const	sys,
		float *const	w,
		const size_t	n,
		const float	initVal )

Set the input delay for LTI system.

Parameters

[in]	sys	A pointer to the LTI system instance
[in]	w	A array of n elements with the delay window for the input channel.
[in]	n	The number of elements of w.
[in]	initVal	The initial value of the input channel.

Returns

1 if the system has been initialized, otherwise return 0.

qLTISys_SetInitStates()

int qLTISys_SetInitStates	(	qLTISys_t *const	sys,
		const float *const	xi )

Set the initial states for the given system.

Precondition

System should be previously initialized by using qLTISys_Setup()

Parameters

[in]	sys	A pointer to the LTI system instance
[in]	xi	An array of n-elements with the initial state values. User can pass NULL as argument to set initial conditions equal to zero.

Returns

1 on success, otherwise return 0.

qLTISys_SetIntegrationMethod()

int qLTISys_SetIntegrationMethod	(	qLTISys_t *const	sys,
		qNumA_IntegrationMethod_t	im )

Set integration method for continuos systems.

Parameters

[in]	sys	A pointer to the continuous LTI system instance
[in]	im	The desired integration method. Use one of the following:

qNumA_IntegralRe : Integrate using the Rectangular rule.

qNumA_IntegralTr : (default) Integrate using the Trapezoidal rule.

qNumA_IntegralSi : Integrate using the Simpson's 1/3 rule.

Returns

1 on success, otherwise return 0.

qLTISys_SetSaturation()

int qLTISys_SetSaturation	(	qLTISys_t *const	sys,
		const float	min,
		const float	max )

Setup the output saturation for the LTI system.

Parameters

[in]	sys	A pointer to the LTI system instance
[in]	min	The minimal value allowed for the output.
[in]	max	The maximal value allowed for the output.

Returns

1 on success, otherwise return 0.

qLTISys_Setup()

int qLTISys_Setup	(	qLTISys_t *const	sys,
		float *	num,
		float *	den,
		void *	x,
		const size_t	nb,
		const size_t	na,
		const float	dt )

Setup and initialize an instance of a LTI system.

Parameters

[in]	sys	A pointer to the continuous LTI system instance
[in,out]	num	: An array of n+1(if continuous) or nb+1(if discrete) elements with the numerator coefficients of the transfer function. Coefficients should be given in descending powers of the n or nb-degree polynomial. Coefficients will be normalized internally.
[in,out]	den	An array of n+1(if continuous) or na+1(if discrete) elements with the denominator coefficients of the transfer function. Coefficients should be given in descending powers of the n or nb-degree polynomial. Coefficients will be normalized internally.
[in,out]	x	Initial conditions of the system. For a continuos system, an array of type qLTISys_ContinuosX_t with n elements. For a discrete system, an array of type qLTISys_DiscreteX_t with max(na,nb) elements For both cases, the supplied array will be updated on every invocation of qLTISys_Excite().
[in]	nb	The order of polynomial num + 1 (Only for discrete systems). example: \( b_{0}+b_{1}z^{-1}+b_{2}z^{-2}+b_{3}z^{-3}, nb = 4 \)

Note

If the system is continuous, pass 0 as argument.

Parameters

[in]

na

The order of polynomial den. (if system is discrete). For continuous system the number of elements of num and den.

example 1: \( a_{0}+a_{1}z^{-1}+a_{2}z^{-2}+a_{3}z^{-3}, na = 3 \)

example 2: \( \frac{ b_{0}s^{2}+b_{1}s+b_{2} }{ a_{0}s^{2} + a_{1}s + a_{2} }, na = 3 \)

Note

For continuous systems, size of num and den should be equal.

Parameters

[in]

dt

The time-step of the continuos system. For discrete systems pass QLTISYS_DISCRETE as argument

Returns

1 on success, otherwise return 0.

Note

By default, initial conditions are set to zero. To change the initial conditions to the desired values, use the qLTISys_SetInitStates() function.