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HN 2020-8-17
评论： Walter Roberson 2020-8-22
I got an error
Output argument "St" (and maybe others) not assigned during call to "get_StCarretero".
Error in InverseVelocityCarretero (line 25)
[St,p]=get_StCarretero(t,P)
Error in RK4_PhRS (line 21)
[k1,~,~,P1,~,~,~,q1] = F(t,th,P,q);
Error in CarreterosPRS_20200812_Velocity (line 24)
[JointValue,Stm,MM,Pose,G,FRK,Rd,q_out,Pd]=
RK4_PhRS(@InverseVelocityCarretero,0,ts,1,th,p,q);
when running the following program.
function [St,p] = get_StCarretero(t,pint)
ts = 1/1000;
rp=1000;
L=1000;
alpha=2*pi/3;
beta=4*pi/3;
A=cos(alpha)-cos(beta);
B=sin(alpha)-sin(beta);
C=(cos(beta)-1)/tan(beta)-(cos(alpha)-1)/tan(alpha);
z=707.1068;
if t==0
x=pint(1);
y=pint(2);
z=pint(3);
else
th=0.2*cos(2*pi*t);
psi=0.2*sin(2*pi*t);
R=A*(cos(th)-cos(psi))+B*cos(th)*sin(psi);
S=A*sin(th)*sin(psi)-B*cos(th)+C*cos(psi);
phi=atan(-R/S);
x=-rp*(cos(th)*cos(phi)+sin(psi)*sin(th)*sin(phi))*cos(alpha)-rp*(-cos(th)*sin(phi)+sin(psi)*sin(th)*cos(phi))*sin(alpha)+(rp/tan(alpha))*(cos(psi)*sin(phi)*(cos(alpha)-1)+cos(psi)*cos(phi)*sin(alpha));
y=-cos(psi)*sin(phi)*rp;
p=[x;y;z]
yaw = phi;
pitch= th;
roll = psi;
vx=diff([x])/ts;
vy=diff([y])/ts;
vz=diff([z])/ts;
droll=diff([psi0,roll])/ts;
dpitch=diff([th0,pitch])/ts;
dyaw=diff([phi0,yaw])/ts ;
JT=[cos(pitch)*cos(yaw) sin(yaw) 0; cos(pitch)*sin(yaw) cos(yaw) 0; -sin(pitch) 0 0];
omg=JT*[dpitch;droll;dyaw];
wx=omg(1);
wy=omg(2);
wz=omg(3);
St =[vx;vy;vz;wx;wy;wz];
end
end
Any help is apperciated
Thank you
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Stephen23 2020-8-17
此评论的直接链接
https://ww2.mathworks.cn/matlabcentral/answers/580452-output-argument-st-and-maybe-others-not-assigned-during-call-to-function#comment_975192
编辑：Stephen23 2020-8-17
When t==0 what values do you allocate to the output arguments St and p ? (hint: none, you do not define them). So what do you expect MATLAB to return when t==0 ?
You need to define some values for St and p for t==0.
HN 2020-8-17
此评论的直接链接
https://ww2.mathworks.cn/matlabcentral/answers/580452-output-argument-st-and-maybe-others-not-assigned-during-call-to-function#comment_975264
编辑：HN 2020-8-17
Thank you so much Stephen Cobeldick ,
Is there any way that I can keep preveous value of x y z to solve diff? It keep reurn zero for St after each iteration.
Thank you
Walter Roberson 2020-8-17
此评论的直接链接
https://ww2.mathworks.cn/matlabcentral/answers/580452-output-argument-st-and-maybe-others-not-assigned-during-call-to-function#comment_975270
x=-rp*(cos(th)*cos(phi)+sin(psi)*sin(th)*sin(phi))*cos(alpha)-rp*(-cos(th)*sin(phi)+sin(psi)*sin(th)*cos(phi))*sin(alpha)+(rp/tan(alpha))*(cos(psi)*sin(phi)*(cos(alpha)-1)+cos(psi)*cos(phi)*sin(alpha));
That looks like a scalar. diff(x) would be empty.
To remember x y z values from previous calls see
persistent
HN 2020-8-17
此评论的直接链接
https://ww2.mathworks.cn/matlabcentral/answers/580452-output-argument-st-and-maybe-others-not-assigned-during-call-to-function#comment_975366
编辑：HN 2020-8-22
When I call get_St3PhRS in another function which has a for loop (RK4_RhPRS), S gives always zero because it doesn't retain previous value to calculate the derivative. I tried to use persistent, but not well implemented. Can you give me some more help?
Thank you
% time function is to create a time vector
function time(t)
persistent n
n=t;
if isempty(n)
n = 0;
end
n = n+1
end
function [Pose, S] = get_St3PhRS(t)
ts=1/1000;
tt=time(t);
rp=1000; % Radius of the base plate in mm
th=-0.2*cos(2*pi*tt);
psi=0.2*sin(2*pi*tt);
z=707.1068;
phi=atan2(sin(psi)*sin(th),(cos(psi)+cos(th)));
T=Rot('y',th)*Rot('x',psi)*Rot('z',phi)
x=1/2*rp*(-cos(phi)*cos(psi)+cos(phi)*cos(th)+sin(phi)*sin(psi)*sin(th));
y=-rp*cos(psi)*sin(phi);
Pose=[x;y;z;th;psi;phi]
% derivative of moving plate rotation angles
vx=gradient(x,ts);
vy=gradient(y,ts);
vz=gradient(z,ts);
dth=gradient(th,ts); %(2*pi*sin(2*pi*t))/5;
dpsi=gradient(psi,ts); %(2*pi*cos(2*pi*t))/5;
dphi=gradient(phi,ts);%(cos(psi)*sigma1*dpsi+cos(th)*dpsi-cos(psi)*sin(psi)*sin(th)*dth)/(-sigma2*sigma1+sigma2+2*cos(psi)*cos(th)+2*sigma1);
JT=[0, cos(th), cos(psi)*sin(th);1, 0, -sin(psi);0, -sin(th), cos(psi)*cos(th)];
dTh=[dth; dpsi;dphi]
w=JT*dTh;
S=[vx;vy;vz;w(1);w(2);w(3)];
end
function [dtheta,Stm,MM,V,G,FRK,R,dq,P] = InverseVelocityPhRs20200820(T,th,~,q)
alpha=2*pi/3;
beta=4*pi/3;
L=1000;
b1 = th(1);
b2 = th(2);
b3 = th(3);
th21 = th(4);
th22 = th(5);
th23 = th(6);
s11=[1;0;0]; % first joint (active) screw of leg 1
s12=[cos(alpha);sin(alpha);0]; % first joint (active) screw of leg 2
s13=[cos(beta);sin(beta);0];
s21=[0;1;0]; % second joint (passive) screw of leg 1
s22=[-sin(alpha);cos(alpha);0]; % second joint (passive) screw of leg 2
s23=[-sin(beta);cos(beta);0];
S=get_St3PhRS(T) % Here is where the function is called
end
function [thout,Stm_out,MM_out,Pout,G_out,FRK_OUT,R_out,q_out,Pd_out] = RK4_RhPRS(F,t0,h,tfinal,y0,p0,q0)
% ODE4 Classical Runge-Kutta ODE solver.
th = y0;
R = eye(3);
P = p0;
q = q0;
q_out=q;
thout = th;
Pout = P;
Pd=[-9.9667;0;707.1068];
Pd_out=Pd;
Stm=[0;0;0;1.1080;0; 0.8593];
Stm_out = Stm;
MM_out = [];
G_out = [];
R_out=R;
FRK=[0;0;0;1.1080;0; 0.8593];
FRK_OUT = FRK;
for t = t0 : h : tfinal-h
[k1,~,~,P1,~,~,~,q1] = F(t,th,P,q); % Error in RK4_RhPRS (line 20)
:
:
end
end
% Main function call
[J,S,M,P,G,F,R,q_out,Pd]= RK4_RhPRS(@InverseVelocityPhRs20200820,0,ts,1,th,P,q);
%% Error
Error using time
Too many output arguments.
Error in get_St3PhRS (line 3)
tt=time(t); % t contains all t values but
Error in InverseVelocityPhRs20200820 (line 19)
S=get_St3PhRS(T)
Error in RK4_RhPRS (line 20)
[k1,~,~,P1,~,~,~,q1] = F(t,th,P,q);
Error in Main3PhRS_20200820 (line 103)
[J,S,M,P,G,F,R,q_out,Pd]= RK4_RhPRS(@InverseVelocityPhRs20200820,0,ts,1,th,P,q);
Walter Roberson 2020-8-22
此评论的直接链接
https://ww2.mathworks.cn/matlabcentral/answers/580452-output-argument-st-and-maybe-others-not-assigned-during-call-to-function#comment_981563
persistent old_x old_y old_z
initializing = (t == 0 || isempty(old_x));
if initializing
do whatever is appropriate for first round
old_x = x;
old_y = y;
old_z = z;
else
do whatever is appropriate for other rounds,
making use of x, y, z, and old_x, old_y, old_z
end
HN 2020-8-22
此评论的直接链接
https://ww2.mathworks.cn/matlabcentral/answers/580452-output-argument-st-and-maybe-others-not-assigned-during-call-to-function#comment_981572
编辑：HN 2020-8-22
Thank you Walter Roberson,
1: Can I initialize all variables like what I did below ? But it gives the error shown below.
Also, list of initialization cause the same result...S=0 vector in each iteration.
2: Why I am unable to accept your answer ?
function [Pose, S] = get_St3PhRS(t)
persistent th0 psi0 phi0 x0 y0 z0
initializing = (t == 0 || isempty(th0,psi0,phi0,x0,y0,z0));
if initializing
ts=1/1000;
rp=1000; % Radius of the base plate in mm
th=-0.2*cos(2*pi*t);
psi=0.2*sin(2*pi*t);
z=707.1068;
phi=atan2(sin(psi)*sin(th),(cos(psi)+cos(th)));
T=Rot('y',th)*Rot('x',psi)*Rot('z',phi)
x=1/2*rp*(-cos(phi)*cos(psi)+cos(phi)*cos(th)+sin(phi)*sin(psi)*sin(th));
y=-rp*cos(psi)*sin(phi);
Pose=[x;y;z;th;psi;phi]
x0=x;
y0=y;
z0=z;
th0=th;
psi0=psi;
phi0=phi;
vx=gradient(x,ts);
vy=gradient(y,ts);
vz=gradient(z,ts);
dth=gradient(th,ts); %(2*pi*sin(2*pi*t))/5;
dpsi=gradient(psi,ts); %(2*pi*cos(2*pi*t))/5;
dphi=gradient(phi,ts);%(cos(psi)*sigma1*dpsi+cos(th)*dpsi-cos(psi)*sin(psi)*sin(th)*dth)/(-sigma2*sigma1+sigma2+2*cos(psi)*cos(th)+2*sigma1);
JT=[0, cos(th), cos(psi)*sin(th);1, 0, -sin(psi);0, -sin(th), cos(psi)*cos(th)];
dTh=[dth; dpsi;dphi]
w=JT*dTh;
S=[vx;vy;vz;w(1);w(2);w(3)];
else
th=-0.2*cos(2*pi*t);
psi=0.2*sin(2*pi*t);
z=707.1068;
phi=atan2(sin(psi)*sin(th),(cos(psi)+cos(th)));
T=Rot('y',th)*Rot('x',psi)*Rot('z',phi)
x=1/2*rp*(-cos(phi)*cos(psi)+cos(phi)*cos(th)+sin(phi)*sin(psi)*sin(th));
y=-rp*cos(psi)*sin(phi);
% derivative of moving plate rotation angles
vx=gradient(x,ts);
vy=gradient(y,ts);
vz=gradient(z,ts);
dth=gradient(th,ts); %(2*pi*sin(2*pi*t))/5;
dpsi=gradient(psi,ts); %(2*pi*cos(2*pi*t))/5;
dphi=gradient(phi,ts);%(cos(psi)*sigma1*dpsi+cos(th)*dpsi-cos(psi)*sin(psi)*sin(th)*dth)/(-sigma2*sigma1+sigma2+2*cos(psi)*cos(th)+2*sigma1);
JT=[0, cos(th), cos(psi)*sin(th);1, 0, -sin(psi);0, -sin(th), cos(psi)*cos(th)];
dTh=[dth; dpsi;dphi]
w=JT*dTh;
S=[vx;vy;vz;w(1);w(2);w(3)];
end
end
Error using isempty
Too many input arguments.
Error in get_St3PhRS (line 3)
initializing = (t == 0 || isempty(th0,psi0,phi0,x0,y0,z0));
Error in InverseVelocityPhRs20200820 (line 19)
S=get_St3PhRS(T)
Error in RK4_RhPRS (line 21)
[k2,~,~,P2,~,~,~,q2] = F(t+h/2,th+h*k1/2,P+h*P1/2,q+h*q1/2);
Error in Main3PhRS_20200820 (line 103)
[JointValue,Stm,MM,Pose,G,FRK,Rd,q_out,Pd]= RK4_RhPRS(@InverseVelocityPhRs20200820,0,ts,1,th,P,q);
Thank you
Walter Roberson 2020-8-22
此评论的直接链接
https://ww2.mathworks.cn/matlabcentral/answers/580452-output-argument-st-and-maybe-others-not-assigned-during-call-to-function#comment_981587
initializing = (t == 0 || isempty(th0) || isempty(psi0) || isempty(phi0) || isempty(x0) || isempty(y0) || isempty(z0));
However, chances are you only need to test one of the variables, because you always set all of the variables after a run, so testing any one of them for emptiness should tell you whether you have already initialized.
HN 2020-8-22
此评论的直接链接
https://ww2.mathworks.cn/matlabcentral/answers/580452-output-argument-st-and-maybe-others-not-assigned-during-call-to-function#comment_981605
编辑：HN 2020-8-22
Walter Roberson, Thank you so much.
Now, things get better. However, the code below always differentiate the current value from initial value. Not previous value. initialized variables always remember the first value than previous one. Where did I make a mistake ?
function [S] = get_St3PhRS(t)
persistent th0 psi0 phi0 x0 y0 z0 vx vy vz w
initializing = (t == 0 || isempty(th0) || isempty(psi0) || isempty(phi0) || isempty(x0) || isempty(y0) || isempty(z0));
if initializing
ts=1/1000;
rp=1000; % Radius of the base plate in mm
th=-0.2*cos(2*pi*t);
psi=0.2*sin(2*pi*t);
z=707.1068;
phi=atan2(sin(psi)*sin(th),(cos(psi)+cos(th)));
T=Rot('y',th)*Rot('x',psi)*Rot('z',phi)
x=1/2*rp*(-cos(phi)*cos(psi)+cos(phi)*cos(th)+sin(phi)*sin(psi)*sin(th));
y=-rp*cos(psi)*sin(phi);
Pose=[x;y;z;th;psi;phi]
x0=x;
y0=y;
z0=z;
th0=th;
psi0=psi;
phi0=phi;
vx=(x-x0)/ts;
vy=(y-y0)/ts;
vz=(z-z0)/ts;
dth=(th-th0)/ts; %(2*pi*sin(2*pi*t))/5;
dpsi=(psi-psi0)/ts; %(2*pi*cos(2*pi*t))/5;
dphi=(phi-phi0)/ts;%(cos(psi)*sigma1*dpsi+cos(th)*dpsi-cos(psi)*sin(psi)*sin(th)*dth)/(-sigma2*sigma1+sigma2+2*cos(psi)*cos(th)+2*sigma1);
JT=[0, cos(th), cos(psi)*sin(th);1, 0, -sin(psi);0, -sin(th), cos(psi)*cos(th)];
dTh=[dth; dpsi;dphi]
w=JT*dTh;
S=[vx;vy;vz;w(1,:);w(2,:);w(3,:)];
else
ts=1/1000;
rp=1000; % Radius of the base plate in mm
th=-0.2*cos(2*pi*t);
psi=0.2*sin(2*pi*t);
z=707.1068;
phi=atan2(sin(psi)*sin(th),(cos(psi)+cos(th)));
T=Rot('y',th)*Rot('x',psi)*Rot('z',phi)
x=1/2*rp*(-cos(phi)*cos(psi)+cos(phi)*cos(th)+sin(phi)*sin(psi)*sin(th));
y=-rp*cos(psi)*sin(phi);
vx=(x-x0)/ts;
vy=(y-y0)/ts;
vz=(z-z0)/ts;
dth=(th-th0)/ts; %(2*pi*sin(2*pi*t))/5;
dpsi=(psi-psi0)/ts; %(2*pi*cos(2*pi*t))/5;
dphi=(phi-phi0)/ts;
JT=[0, cos(th), cos(psi)*sin(th);1, 0, -sin(psi);0, -sin(th), cos(psi)*cos(th)];
dTh=[dth; dpsi;dphi]
w=JT*dTh;
S=[vx;vy;vz;w(1);w(2);w(3)];
end
end
Walter Roberson 2020-8-22
此评论的直接链接
https://ww2.mathworks.cn/matlabcentral/answers/580452-output-argument-st-and-maybe-others-not-assigned-during-call-to-function#comment_981644
After you have done the calculations, but before you return, you need to update x0, y0, z0 with the current x, y, z.
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