lsiminfo
Compute linear response characteristics
语法
说明
lsiminfo lets you compute linear response characteristics from an array of response data [y,t]. For a linear response y(t), lsiminfo computes characteristics relative to yinit and yfinal, where yinit is the initial offset, that is, the value before the input is applied, and yfinal is the steady-state value of the response.
lsiminfo uses yinit = 0 and yfinal = last sample value of y(t) unless you explicitly specify these values.
The function returns the characteristics in a structure containing the fields:
TransientTime— The first time T such that the error |y(t) – yfinal| ≤ SettlingTimeThreshold × emax for t ≥ T, where emax is the maximum error |y(t) – yfinal| for t ≥ 0.By default, SettlingTimeThreshold = 0.02 (2% of the peak error). Transient time measures how quickly the transient dynamics die off.
SettlingTime— The first time T such that |y(t) – yfinal| ≤ SettlingTimeThreshold × |yfinal – yinit| for t ≥ T.By default, settling time measures the time it takes for the error to stay below 2% of |yfinal – yinit|.
Peak— Peak value of |y(t) – yinit|. (自 R2025a 起)PeakTime— Time at which the peak value occurs. (自 R2025a 起)Min— Minimum value of y(t).MinTime— Time the response takes to reach the minimum value.Max— Maximum value of y(t).MaxTime— Time the response takes to reach the maximum value.
For complex responses, lsiminfo computes characteristics based on the magnitudes of the complex values in y, yinit, and yfinal. (自 R2025a 起)
S = lsiminfo(y,t)y and corresponding time vector t. This syntax uses yinit = 0 and the last value in y (or the last value in each channel's corresponding response data) as yfinal to compute characteristics that depend on these values.
For SISO system responses, y is a vector with the same number of entries as t. For MIMO response data, y is an array containing the responses of each I/O channel.
S = lsiminfo(y,t,yfinal)yfinal. This syntax is useful when you know that the expected steady-state system response differs from the last value in y for reasons such as measurement noise. This syntax uses yinit = 0.
For SISO responses, t and y are vectors with the same length NS. For systems with NY outputs, you can specify y as an NS-by-NY array and yfinal as an NY-by-1 array. lsiminfo then returns a NY-by-1 structure array S of response characteristics corresponding to each output channel.
S = lsiminfo(y,t,yfinal,yinit)yinit. This syntax is useful when your y data has an initial offset, that is, y is nonzero before the input is applied.
For SISO responses, t and y are vectors with the same length NS. For systems with NY outputs, you can specify y as an NS-by-NY array and yfinal and yinit as an NY-by-1 arrays. lsiminfo then returns a NY-by-1 structure array S of response characteristics corresponding to each output channel.
S = lsiminfo(___,'SettlingTimeThreshold', lets you specify the threshold ST)ST used in definition of settling and transient times. The default value is ST = 0.02 (2%). You can use this syntax with any of the previous input-argument combinations.
示例
Create the following continuous-time transfer function:
sys = tf([1 -1],[1 2 3 4]);
Calculate the impulse response.
[y,t] = impulse(sys);
impulse returns the output response y and the time vector t used for simulation.
Compute the response characteristics using a final response value of 0.
s = lsiminfo(y,t,0)
s = struct with fields:
TransientTime: 22.8700
SettlingTime: NaN
Peak: 0.4268
PeakTime: 2.0088
Min: -0.4268
MinTime: 2.0088
Max: 0.2847
MaxTime: 4.0733
You can plot the impulse response and verify these response characteristics. For example, the time at which the minimum response value (MinTime) is reached is approximately 2 seconds.
impulse(sys)
