myGL

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14 years, 305 days
Dr. Gilbert Lai is an independent consultant. He is also a mentor for FIRST Robotics team SWAT 771 (http://swat771.com). As a former employee of Maplesoft, he was team lead in the MapleSim simulation engine development team and was technical adviser on various MapleSim add-on toolboxes.

Trained as a Computer Engineer, Dr. Lai’s research interests include robotics control (force feedback teleoperation), aerospace and mechatronics applications (helicopter modelling and control). In his spare time, he enjoys computer games, Sci-Fi movies and quality time with his family.

You can follow @gilbert_lai_phd on Twitter.

MaplePrimes Activity


These are replies submitted by myGL

No credit will be claimed for my team on the shooter design, of course, as we did not "reinvent the wheel" :)

==============================

Gilbert Lai, PhD

@dkhramov 

 

I used the extra rigid body frame to adjust the orientation of the base frame of reference, which is used to measure the joint angle from.  Think about it as an offset to your sensor measurement data.  It is relevant only with respective to which axis you want as your reference axis for measuring the angle (i.e. either x or y) and whether your rod orientation is along x or y direction.

 

If you find that you sensor measurement is what you expect it to be, there is no need to add the extra rigid body frame.

 

Hope this helps.

 

Cheers,

Gilbert

@dkhramov 

 

I used the extra rigid body frame to adjust the orientation of the base frame of reference, which is used to measure the joint angle from.  Think about it as an offset to your sensor measurement data.  It is relevant only with respective to which axis you want as your reference axis for measuring the angle (i.e. either x or y) and whether your rod orientation is along x or y direction.

 

If you find that you sensor measurement is what you expect it to be, there is no need to add the extra rigid body frame.

 

Hope this helps.

 

Cheers,

Gilbert

Also, which version of MapleSim does this happen to?

 

Thanks!

 

==============================

Gilbert Lai, PhD

Senior Applications Engineer, R&D Applications Engineering

Maplesoft

If not, can you send us the model so we can help investigate why it is running slowly for you.

 

Alternatively, if you are unable to send us the model, can you at least send us the log message (from the console window in the bottom) when running the simulation with Verbose mode. That should at least give us some indication of the breakdown of the timing within the simulation engine (from which, hopefully, we can find out why the model runs slowly).

 

Thanks!

 

==============================

Gilbert Lai, PhD

Senior Applications Engineer, R&D Applications Engineering

Maplesoft

@Joe Riel 

 

I suppose we could use the Dot Product (?componentLibrary/signalBlocks/math/operators/DotProduct) to get the r^2 term directly instead of computing r with the Vector Norm block and then squaring it...

@Joe Riel 

 

I suppose we could use the Dot Product (?componentLibrary/signalBlocks/math/operators/DotProduct) to get the r^2 term directly instead of computing r with the Vector Norm block and then squaring it...

Here is the link to the MapleSim help page for the flexible beam component:

 

?componentLibrary/multibody/bodiesAndFrames/FlexibleBeam 

 

 

==============================

Gilbert Lai, PhD

Senior Applications Engineer, R&D Applications Engineering

Maplesoft

Here is the link to the MapleSim help page for the flexible beam component:

 

?componentLibrary/multibody/bodiesAndFrames/FlexibleBeam 

 

 

==============================

Gilbert Lai, PhD

Senior Applications Engineer, R&D Applications Engineering

Maplesoft

This is another me-too for the time out problem. I am using FireFox 1.5.0.1 on Windows 2000. (Where, if there is such option available, and what should I do to setup my browser so I don't see any timeout?) Thanks! Gilbert ================================ Applications Engineer, Maplesoft
I am not sure if this is relevant, but Maple 10 comes with a Maple Calculator (if you are using Windows, an icon should be installed on your desktop). In the calculator, you can specify the use of degrees instead of radians under the Setting tab. Hope this helps! Gilbert ================================ Applications Engineer, Maplesoft
I am not sure if this is relevant, but Maple 10 comes with a Maple Calculator (if you are using Windows, an icon should be installed on your desktop). In the calculator, you can specify the use of degrees instead of radians under the Setting tab. Hope this helps! Gilbert ================================ Applications Engineer, Maplesoft
I agree with Joe.
Your commands seem to be running fine under Maple 9.5.
What is the problem?

> restart;

> with(inttrans);

Maple Equation

> y:=(2.5)/((8*s^2+6*s+1)*s);

Maple Equation

> y1:=invlaplace(y,s,t);
plot(y1,t=0..25);

Maple Equation

Maple Plot

> y:=(2.5*exp(-1.5*s))/((8*s^2+6*s+1)*s);
y1:=invlaplace(y,s,t);
plot(y1,t=0..25);

Maple Equation

Maple Equation

Maple Plot

> ode := 8*(diff(x(t), t, t))+6*(diff(x(t), t))+x(t) = 2.5*Heaviside(t-1.5);
ics := x(0) = 0, (D(x))(0) = 0;
sol := dsolve({ics, ode}, x(t), numeric, stiff = true, range = 0 .. 25);
plots[odeplot](sol);

Maple Equation

Maple Equation

Maple Equation

Maple Plot

>

This post generated using the online HTML conversion tool
Download the original worksheet

Gilbert
================================
Applications Engineer, Maplesoft
I agree with Joe.
Your commands seem to be running fine under Maple 9.5.
What is the problem?

> restart;

> with(inttrans);

Maple Equation

> y:=(2.5)/((8*s^2+6*s+1)*s);

Maple Equation

> y1:=invlaplace(y,s,t);
plot(y1,t=0..25);

Maple Equation

Maple Plot

> y:=(2.5*exp(-1.5*s))/((8*s^2+6*s+1)*s);
y1:=invlaplace(y,s,t);
plot(y1,t=0..25);

Maple Equation

Maple Equation

Maple Plot

> ode := 8*(diff(x(t), t, t))+6*(diff(x(t), t))+x(t) = 2.5*Heaviside(t-1.5);
ics := x(0) = 0, (D(x))(0) = 0;
sol := dsolve({ics, ode}, x(t), numeric, stiff = true, range = 0 .. 25);
plots[odeplot](sol);

Maple Equation

Maple Equation

Maple Equation

Maple Plot

>

This post generated using the online HTML conversion tool
Download the original worksheet

Gilbert
================================
Applications Engineer, Maplesoft
The short answer to your question "can you solve it in general?" is probably no. And that's not a Maple thing. It is more the nature of the problem. In general, inverse kinematic problems either do not have a solution (e.g. the desired position is outside of the robot arm workspace), only a sinlge solution (at singularity) or it has multiple solutions (elbow up/down configuration). So depending on the values of the unknown parameters, the same problem could have one, multiple or no solution at all. This is why I doubt you can solve the problem "symbolically" (with no assumption on the unknowns). For special cases, where you can apply knowledge of the geometric configuration of the robot for simplication, you might be able solve the inverse kinematic problem symbolically. Other than that, you are probably better off substituting in all of the parameters and solve the problem numerically. Gilbert ================================ Applications Engineer, Maplesoft
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