Better way to implement real-time user input into simulation?

Question

BreezyWest 2018-11-27

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/432402-better-way-to-implement-real-time-user-input-into-simulation

From browsing the other posts about getting user input to play nicely with running scripts, it seems a common way to accomplish this is by utilizing the 'WindowKeyPressFcn' and similar properties of figures. That is what I have implemented below. The code simulates a particle in 1D space with an ODE of

where F is toggled between -1, 1, and 0 depending on if the left arrow key, right arrow key, or no key is pressed. This is done by checking the event value of 'WindowKeyPressFcn' and 'WindowKeyReleaseFcn' and assigning an X value to a secondary plot (a single point) via fig.CurrentAxes.Children(1).XData, since this is a value that the script has access to at all times, regardless of what figure is active. The defined ODE function, f, then extracts this value for F.

My question: Is there a cleaner way to send input data to the ODE function, f, rather than having to use another plot in the figure? Is the way of handling user input the best way of having an interactive figure using the keyboard (as apposed to a formal GUI)?

Obviously the way I've used works, but in trying to improve my Matlab skills I would like to take advantage of not having to reinvent the wheel.

dt = 0.05; %Solver timestep
y = [0; 0]; %initial position and velocity
Pos = NaN(10000,1);
Vel = NaN(10000,1);
fig2 = figure(2); %Phase space plot
p0 = plot(Pos,Vel);
xlabel('Position');
ylabel('Velocity');
fig = figure(1); %Only use figure 1
p1 = scatter(0,0); hold on %p1 is free moving body (blue)
p2 = scatter(0,0.25); hold off %P2 is force applied (orange)
xlim([-5 5])
ylim([-0.5 0.5])
set(fig,'WindowKeyPressFcn',@keyPressFun); %Set force to -1/1 for left/right arrow keys 
set(fig,'WindowKeyReleaseFcn',@keyReleaseFun); %Set force to zero when released
t_cur = 0;
Tit = title('','FontName','Courier New');
n = 1;
while 1
    y = RK4(@f,y,dt,t_cur); %Solve system
    p1.XData = y(1); %Update free body location
    if mod(n,3) == 0
        m = n/3;
    p0.XData(m) = y(1);
    p0.YData(m) = y(2);
    end
    pause(0.005) %Delay to avoid breaking computer
    t_cur = t_cur + dt; %Update time
    Tit.String = [num2str(1/2*5*y(2)^2+1/2*1*y(1)^2,5) ' ' num2str(n)]; %Total Energy of system as title
    n = n+1;
end
function dy = f(t,y) %System ODE
fig = figure(1);
F = fig.CurrentAxes.Children(1).XData; %Get force value from reference point
M = 5; %Mass
C = 0.15; %Damping
K = 1; %Stiffness
dy = zeros(2,1); %Preallocate output
dy(1) = y(2); %Get velocity
dy(2) = -K/M*y(1) - C/M*y(2)^2*sign(y(2))+F/M; %Get acceleration
end
%Runga Kutta 4th order
function [y_next] = RK4(f,y_cur,dt,t_cur)
k1 = f(t_cur         ,y_cur          );
k2 = f(t_cur + 0.5*dt,y_cur+0.5*dt*k1);
k3 = f(t_cur + 0.5*dt,y_cur+0.5*dt*k2);
k4 = f(t_cur +     dt,y_cur+    dt*k3);
y_next = y_cur+1/6*(k1 + 2*k2 + 2*k3 + k4)*dt;
end
%Set X coord of reference point to 1 or -1 depending on
%what key is pressed. Used for force
function keyPressFun(source,eventdata)
keyPressed = eventdata.Key;
fig = gcf;
if strcmpi(keyPressed,'rightarrow')
    fig.CurrentAxes.Children(1).XData = 1;
elseif strcmpi(keyPressed,'leftarrow')
    fig.CurrentAxes.Children(1).XData = -1;
end
end
%Set X coord of reference point to 0 when key is released
function keyReleaseFun(source,eventdata)
keyPressed = eventdata.Key;
fig = gcf;
fig.CurrentAxes.Children(1).XData = 0;
end