MATLAB: Why I am getting error while tuning using control system tuner

controlControl System Toolboxcontrol system tuningmimoroboitcsRobotics System ToolboxSimscapesimulinkSimulink Control Design

While I am trying to select signals for quick loop tuning, I am getting on this error repeatedly. I don't fully understand how can t can be negative during simulatiion and error raised by the above image. Can anyone please explain

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MATLAB: How can i solve an equation with an integral when the upper bound is the unknown variable

Hi,

If:

- all variables except t (upper bound) are known,

- assuming that Walter (as usual) is right with his commentary and that arcsine is meant instead of a * sin

- and RO = Ro

you can solve it like this:

syms R2 RO a Ro t vx_t0 vy_t0 t0 vx_t1 vy_t1 t1
f = asin((R2+RO)*sin(a)/(2*RO))*RO == int(t1*sqrt(vx_t1^2+vy_t1^2)) - int(t0*sqrt(vx_t0^2+vy_t0^2))

divides the integral into the upper - lower bound with the corresponding variables. When solving for t1 and simplifying the result you get:

sol_t1 = t1 == simplify(solve(f,t1))

or as a function handle:

t1_fun = @(R2,RO,a,t0,vx_t0,vx_t1,vy_t0,vy_t1)(RO.*asin((sin(a).*(R2+RO).*(1.0./2.0))./RO).*2.0+t0.*vy_t0.^2.*log(vx_t0+sqrt(vx_t0.^2+vy_t0.^2))+t0.*vx_t0.*sqrt(vx_t0.^2+vy_t0.^2))./(vx_t1.*sqrt(vx_t1.^2+vy_t1.^2)+vy_t1.^2.*log(vx_t1+sqrt(vx_t1.^2+vy_t1.^2)))

Of course, this only works if the above conditions are met. Then you can calculate your upper limit (here: t1) in this way.

Best regards

Stephan

MATLAB: Getting an error of ‘Reference to non-existent field’

The way traj_generator is coded, when t is 0, it returns a structure with only 3 fields: pos, yaw and yawdot (these last two are always 0). It's only when t is not 0 that it creates the fields vel and acc.

So, indeed if t is 0 and you try to use the vel field you'll get your error. Either you mustn't use vel or acc if t is 0, or you must modify traj_generator so that it creates these fields even when t is 0:

%original code in traj_generator
        if(t == 0)
            desired_state.pos = waypoints0(:,1);
        else

replace with

        if t == 0   %brackets were completely unnecessary
            desired_state.pos = waypoints0(:,1);
            desired_state.vel = ????;  %no idea what you want there

            desired_state.acc = ????;  %no idea what you want there
        else
            %...

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MATLAB: How can i solve an equation with an integral when the upper bound is the unknown variable

MATLAB: Getting an error of ‘Reference to non-existent field’

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