I am currently designing a Simscape Multibody model of my drone. My drone is a three-armed device, which somewhat resembles the rotors of a helicopter.
The drone is supposed to rotate around itself, using a motor on each arm. Furthermore, each arm will have a wing attached to produce the lift required.
The initial purpose will be to control the RPMs of the motors as well as the pitch of the wings.
Currently I have a model without the wings, so I am looking for a way to model wings that do have some aerodynamic properties, that would be able to create some force upwards (lift) from the spinning motion.
How can I integrate wings (or other forms of artificial lift) in to my model?
3D Model of the drone with motors (generated from Simulink)
You have several options:
A) Use Aerospace Blockset for ready-to-use aerodynamic forces
B) Compute your own simplified aerodynamic forces (with Simscape Physical-Signal blocks or Simulink blocks) based on relative orientation, cross-sectional area and speed of your solid wrt the air.
Both options would require sensing the relative orientation and speed of the drone, using the sensing option on the 6-DOF Joint.
Here's an example of using Simscape Multibody together with Aerospace Blockset, but for ground vehicles.
Related
I have imported Cad models of a mechanical system to Simscape multibody.
I need to reflect the effect of some physical parameters (like temperature, pressure...) on the surface of the parts of the system, such that their color changes according to the level of the parameter.
Are there any specific methods that could help me to achieve this step?
Im simulating a swing door with generator using Simscape/Simulink. I imagine there is only one input for system which is the force at the knob needed to open the door, so all revolute joints have their torque actuation set to automatically computed. However, im getting an error saying:
"In the dynamically coupled component containing Revolute Joint 'SDL/SwingMotion', there are more joint primitive degrees of freedom with automatically computed force or torque (4) than with motion from inputs (0). In general, the equations of motion do not have a unique solution. Solve this problem by increasing the number of joint primitives with motion from inputs or reducing the number of joint primitives with automatically computed force or torque. Resolve this issue in order to simulate the model."
The animation works fine if i set the torque actuation of all 4 revolute joints to none, but the torque produced by the force wont be transfered this way and the generator shaft wont have any torque. However, I am able to measure the output RPM (angular velocity of generator shaft). I dont quite understand the error. Why do the revolute block treats the degree of motion of other revolute blocks as its own? How do i resolve this?
Block Diagram can be seen here.
The Assembly looks like this:
Any help is much appreciated!
For a revolute joint there are three options:
Let the revolute joint just act as a hinge, no torque can be exerted from base to follower and vice versa
Provide torque and calculate motion from the torque. This is called forward dynamics, motion is determined from torque.
Provide motion and calculate torque from the motion. This is called inverse dynamics, torque is determined from motion.
So you have to select either one of the option. If you select torque automatically computed, then you need to provide the motion which it has to follow. If you don't need to follow a provided motion, than no torque is needed.
If you set torque computed to 'none', then there is no torque that can be exerted from the base to the follower and vice versa, that is the idea of a Degree of Freedom.
It seems as if you want the Base and the Follower to be somewhat rigidly connected and follow the same motion. Than you can consider using the Rigid Transform block, which is just a rigid link in which you can define a translation or rotation offset.
EDIT
What you were effectively doing was combining forward and inverse dynamics. You put a force on the doorknob, let Simulink calculate the motion (up till now forward dynamics) then you desire the torque on the GenShaft from the motion it is doing, which is inverse dynamics. That does not work.
A better way to check the torque on the GenShaft is to, for instance, desire a certain door hinge angular velocity, put a proportional controller on it, and check the required torque. Notice that with no friction modeled in the hinge the required torque will go to zero.
So if you set all torque computed to 'none' except for the GenShaft, set this to provided by input. Then put a proportional controller on the angular velocity of the door hinge. You can then check the torque needed.
Updated model
I am making a game in Unity that involves creatures whose animations are determined by physics. For example, to move a limb of a creature, I can apply forces to the rigidbody it's associated with. I know how to apply forces programmatically through a script to create movements, but I'd like to create more complex and organic movements and thought that I might be able to use a neural network to do this.
I'd like each of the creatures to have a distinct way of moving in the world. I'd like to first puppeteer the creatures manually using my hand (with a Leap Motion controller), and have a neural network generate new movements based on the training I did with my hand.
More concretely, my manual puppeteering setup will apply forces to the rigidbodies of the creature as I move my hand. So if I lift my finger up, the system would apply a series of upward forces to the limb that is mapped to my finger. As I am puppeteering the creature, the NN receives Vector3 forces for each of the rigidbodies. In a way this is the same task as generating a new text based on a corpus of texts, but in this case my input is forces rather than strings.
Based on that training set, is it possible for the NN to generate movements for the characters (forces to be applied to the limbs) to mimic the movements I did with my hand?
I don't have that much experience with neural networks, but am eager to learn, specifically for this project. It would be great to know about similar projects that were done in Unity, or relevant libraries I could use that would simplify the implementation. Also, please let me know if there is anything I can clarify!
Not really an answer but would not fit for comments
I'm not sure the strategy you want to apply to train your model is the right one.
I would go for reinforcement learning methods (you can check this question for more infos about it) using, for example, the distance traveled by the center of mass of the creature on the x-axis as a fitness. If this leads to weird behaviours (like this well known robot) you could, for example, think of strategies like penalizing your individuals given the distance traveled on y and z axis (still by the CoM) to try having guys that keep there CoM on the same plane.
Without knowing exactly what you want to achieve this is hard to give you more advices. Although, if you are not looking only for neural network based techniques, there is this really great paper you might want to have a look at (here is the video of their results).
I am new to Simulink and I am having some problems on building and running multibody models.
Shortly, here is my problem.
I have designed a 2 joint,2 body system. I actuate each joint with position, velocity and acceleration data (array format) and the system works perfectly. I connected joint sensors to each joint, torque produced by joints are saved to workspace. I have the same model but it analyzes the system in forward dynamics. So, joints in this model are actuated by torques obtained from inverse dynamics model. But the motion comes out from the forward dynamics model is not same with the inverse dynamics model, even it is not similar, it is completely absurd. I think I have checked everything but for sure not "everything". Can anyone help me in this?!
I think it would be fun to model a top view of a train following a track, traversing switches and so on, using a physics library like Box2D. What joints and motors would I need to make this work?
I'm curious about how to implement the forces needed to make the car follow a spline track so it can bump into other train cars, pedestrians, DeLoreans etc. Just saying "the car is now at spline(t)" for each time step would create excessive forces in the physics engine. If I understand correctly, you have to stick the car onto the track with one force, constrain its angle to tend towards parallel with the track with another (or stick the front and back of the car to the track with two forces), and create another force to propel the train forward. I'm looking for some details on how to accomplish these things.
I believe it would be easier without "real" physics, like the ball movement of games such as Luxor or Tumble Bugs. Meaning: let the train follow a spline which is defined by the tracks.
Using phyiscs is probably overkill to make a train follow a track and could lead to all kinds of undesired side-effects, including jerky motion, train derailing, train getting stuck on junctions, etc.
You could still join the individual wagons together using physic joints, however. Just make sure that only the locomotive gets acceleration forces, the rest of the train just follows or is pushed but stays on the spline.
Why are you worried about keeping it "on the tracks"? Where is it going to go? Gravity should keep it down, object intersection should keep it up, and so the only directions you need to worry about are forward and backwards. That's where a motor comes in, and you're done. The rest is decorations.
In response to edit of problem:
Siderails. And have the train long enough / rigid enough compared to its width that you can navigate crossings (make them closer to right angles to minimize the crossing problems.
A top-down view (i.e. seeing the train from the sky) doesn't really require a 2d physics engine - if I understand you correctly. In fact, it seems like it wouldn't really help with the problem (if you want a train simulation), but then maybe you just wanna try it out for fun. :)
However, what about putting something like a slider joint on the train and the cars, and a motor on the locomotive. The slider joint might need some special implementation; you probably want to run the train along a spline and not a segment of straight lines, right?
Some sort of ball joint would connect the cars together.
The implementation is not so toughand I was able to prototype something in a few hours that does the basic job. It will require a lot of work to make it run smoothly, but it's essentially just "siderails."
Being top-down you obviously first must turn off gravity in Box2D. Second, build a train. Treat train wheels like car wheels and it'll suddenly get a lot more simple. For tracks you have a few choices:
Create your own game object (not in the box2D world) that is a simple line the train will then "follow" (you can use motors on train wheels to "steer" towards the line). Then just overlay the line with some nice wide "rail" graphics and you have a nicely faked system. Tell the wheels to turn off if it strays too far from the line and presto, you have a derailment.
Create actual physical rails - outside rails (like siderails) that the trains "wheels" will bump into. They will have to have gentle curves in this instance, which could be very difficult given the limited resources you have (simulating a nice slow curve out of boxes in Box2D is rough on the processor)
Then just let your train go!