CODEWITHSUNDEEP
matlabsimulink
Sam A
Sam A

Reputation: 1

Input equations into Matlab for Simulink Function

I am currently working on an assignment where I need to create two different controllers in Matlab/Simulink for a robotic exoskeleton leg. The idea behind this is to compare both of them and see which controller is better at assisting a human wearing it. I am having a lot of trouble putting specific equations into a Matlab function block to then run in Simulink to get results for an AFO (adaptive frequency oscillator). The link has the equations I'm trying to put in and the following is the code I have so far:

    function [pos_AFO, vel_AFO, acc_AFO, offset, omega, phi, ampl, phi1] = LHip(theta, eps, nu, dt, AFO_on)
            t = 0;
            % syms j
            % M = 6;
            % j = sym('j', [1 M]);

            if t == 0
                omega = 3*pi/2;
                theta = 0;
                phi = pi/2;
                ampl = 0;
            else
                omega = omega*(t-1) + dt*(eps*offset*cos(phi1));
                theta = theta*(t-1) + dt*(nu*offset);
                phi = phi*(t-1) + dt*(omega + eps*offset*cos(phi*core(t-1)));
                phi1 = phi*(t-1) + dt*(omega + eps*offset*cos(phi*core(t-1)));
                ampl = ampl*(t-1) + dt*(nu*offset*sin(phi));
                offset = theta - theta*(t-1) - sym(ampl*sin(phi), [1 M]);
            end
    
            pos_AFO = (theta*(t-1) + symsum(ampl*(t-1)*sin(phi*        (t-1))))*AFO_on; %symsum needs input argument for index M and range
            vel_AFO = diff(pos_AFO)*AFO_on;
            acc_AFO = diff(vel_AFO)*AFO_on;
    end

https://www.pastepic.xyz/image/pg4mP

Essentially, I don't know how to do the subscripts, sigma, or the (t+1) function. Any help is appreciated as this is due next week

Upvotes: 0

Views: 315

Answers (1)

Mouse On Mars
Mouse On Mars

Reputation: 1132

You are looking to find the result of an adaptive process therefore your algorithm needs to consider time as it progresses. There is no (t-1) operator as such. It is just a mathematical notation telling you that you need to reuse an old value to calculate a new value.

omega_old=0;
theta_old=0;
% initialize the rest of your variables

for [t=1:N]
   omega[t] = omega_old +  % here is the rest of your omega calculation
   theta[t] = theta_old +  % ...

   % more code .....

   % remember your old values for next iteration
   omega_old = omega[t];
   theta_old = theta[t];
end

I think you forgot to apply the modulo operation to phi judging by the original formula you linked. As a general rule, design your code in small pieces, make sure the output of each piece makes sense and then combine all pieces and make sure the overall result is correct.

Upvotes: 1

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