Generate MATLAB code for tunable gain surfaces
Create a tunable surface that represents a scalar gain with a bilinear dependence on two scheduling variables. Suppose that the scheduling variables are
alpha, ranging from 0-15 degrees, and
V, ranging from 300-600 m/s. The tunable surface covers a linearly spaced grid in this operating range.
[alpha,V] = ndgrid(0:3:15,300:50:600); domain = struct('alpha',alpha,'V',V); shapefcn = @(x,y) [x,y,x*y]; GS0 = tunableSurface('K',1,domain,shapefcn);
Usually, you use
GS0 to parameterize a scheduled gain and tune the surface coefficients with systune. For this example, instead of tuning, manually set the coefficients to non-zero values.
GS = setData(GS0,[100,28,40,10]);
Generate MATLAB code that computes the scalar gain as a function of scheduling variables.
code = codegen(GS)
code = 'function Gain_ = fcn(alpha_,V_) %#codegen % Type casting ZERO = zeros(1,1,'like',alpha_+V_); alpha_ = cast(alpha_,'like',ZERO); V_ = cast(V_,'like',ZERO); % Tuned gain surface coefficients Coeffs = cast([100 28 40 10],'like',ZERO); Offsets = cast([7.5 450],'like',ZERO); Scalings = cast([7.5 150],'like',ZERO); % Normalization alpha_ = (alpha_ - Offsets(1))/Scalings(1); V_ = (V_ - Offsets(2))/Scalings(2); % Compute weighted sum of terms Y = [ alpha_ , V_ , alpha_*V_ ]; Gain_ = Coeffs(1); for i=1:numel(Y) Gain_ = Gain_ + Coeffs(i+1) * Y(i); end '
The resulting code is a function,
fcn, that takes two scheduling variables and returns a scalar gain. The function includes the
%#codegen directive, so that it can be used for further code generation, such as implementing a tuned gain schedule in hardware.
The function includes four sections. The first section ensures that the scheduling variables are cast to the same type. The second section encodes the gain coefficients and the offsets and scalings that the software extracts from
GS. These values are hard-coded into
fcn, which can compute the gain surface without reference to G
S. The third section uses these values to compute the normalized scheduling variables. (See
tunableSurface for more information about normalization.)
The last section computes the gain by summing up all the terms in the polynomial expression for the gain surface.
GS— Tunable gain surface
Tunable gain surface, specified as a
code— Generated code for gain surface
Generated code for the gain surface, returned as a character array. The
code contains a function,
Gain_ = fcn(x1_,x2_,...,xN_),
that computes the gain from the scheduling variables
expression relating the gain to the scheduling variables, the coefficients
of the expression, and the normalization of the scheduling variables are all
GS, and the code can run without further
TS. The returned function includes the
%#codegen directive so that it can be used for
further code generation, such as implementing a tuned gain schedule in
When you use
writeBlockValue to write tuned
gain-surface coefficients from an
slTuner interface to
a MATLAB Function block, it uses this generated MATLAB code.