30
votes
Accepted
Robot never goes straight
I'm posting this as an answer because it is the answer.
You can't.
As @BendingUnit22 mentions, you are attempting "open loop" control. Noise and variations will mean that your robot will never ...
- 15.9k
17
votes
Position Control vs Velocity Control vs Torque Control
I'm going to take a slightly different tack to Chuck.
What is Torque Control?
For me, Torque Control is about performing a move with an explicitly defined torque, rather considering torque just the ...
- 4,213
15
votes
Position Control vs Velocity Control vs Torque Control
Torque is analogous to force for rotating systems, in that:
$$
F = m a \\
\tau = I \alpha \\
$$
Where $\alpha$ is angular acceleration and $I$ is moment of inertia. $m$ and $a$ are mass and linear ...
- 15.9k
13
votes
What's the difference between feedback and feedforward control?
In the simple models and block diagrams of control systems you will find in basic textbooks, they will show you a single diagram with a feedback section which uses measurements of the target parameter ...
- 4,335
11
votes
Accepted
Quadcopter PID Algorithm
The glaring issue I see at the moment is that you are forcing polarity on the I and D terms. In general, you are using a lot of sign checks, sign assignments, and conditional programming.
None of that ...
- 15.9k
11
votes
Accepted
Control VS artificial intelligence?
In robotics, it all boils down to making the hardware(in essence, the actuator) perform the desired action. The basics of control systems tell us that the transfer function decides the relationship ...
- 671
10
votes
Accepted
How can we use the accelerometer for altitude estimation?
The barometer carried on the pixhawk has an altitude resolution of 10 cm. If that isn't enough, you could write a kalman filter that uses the accelerometer data in the prediction step and the ...
- 1,833
10
votes
Accepted
How to create a Industrial Robotic arm controller?
Industrial robots (e.g. Kuka, ABB, Fanuc) use a control cabinet which has the following main components:
Drive amplifiers (controllers):
The drive amplifiers are responsible for the closed loop ...
- 6,632
10
votes
Accepted
What is the terminology used to describe control without measurement?
In control theory, we refer to this as "open-loop control", which emphasizes the lack of a feedback loop.
The wikipedia article has several examples of open-loop control.
- 166
9
votes
Accepted
How to tune the PID parameters using Fuzzy Logic?
The paper Controlling of Quadrotor UAV Using a Fuzzy System for Tuning the PID Gains in Hovering Mode by E. Abbasi, M. J. Mahjoob explains how to tune PID gains with fuzzy logic. You can find many ...
- 1,104
9
votes
What is the technology used for no-resistance robot arms?
It's called compliance. Gravity compensation by itself is not enough to achieve this, as well it is not mandatory. For example, if reducers with high reduction ratios are used, robot arm will be very ...
- 241
9
votes
Accepted
Multiple control loops with overlapping effects
Typically with a multiple input, multiple output (MIMO) system, a control engineer uses a state feedback controller. This style of controller leverages a state-space model of the system and generally ...
- 15.9k
9
votes
Accepted
How do I determine the required encoder resolution for a control system?
First I would question your math that got you to the 12b sensor.
If you have a $dy$ of 1 mm over an arm that is $r = 1$ m long, then $\sin(\theta) = dy/r \rightarrow \theta = \mbox{asin}(dy/r)$. If ...
- 15.9k
9
votes
Accepted
How to approach any advanced control problem in robotics
Models.
If you want to get good at control engineering, get good at modeling. If you want to impress a controls professor, get good at modeling. Models are how you're going to do 90 percent of your ...
- 15.9k
9
votes
Accepted
Impedance Control vs Position Control
In classical position control, the feedback controller only cares about the position error and is tuned to minimize it. This is done by using very high gains, i.e. if there is even a small position ...
- 106
8
votes
What is $\alpha \sin(\theta) + \beta \frac{d \theta}{d t}$ in the inverted pendulum problem?
The function $f$ comes from the equation of motion for the inverted pendulum problem (inverted pendulum alone, not including the motion of the wheeled platform). If you consider your figure but ignore ...
- 1,377
8
votes
Using genetic algorithm for tuning controllers
Genetic algorithms are a machine learning technique to remove the need for a user to 'fine tune' a system, and instead allow a computer to figure out how to tune the system. The benefits of this ...
- 81
8
votes
Accepted
Can a state matrix have a row of zeros?
Yes, a state matrix with zero rows and/or columns makes sense and is viable. It typically signify pure integrators in the system. In the example you give,
$$
\dot{v} = -\frac{b}{m} v +\frac{1}{m} u
...
- 385
8
votes
Motion Planning vs. Control
There is a saying in software engineering which states that your company structure is reflected in your software architecture (I cannot recall the exact phrase). This is true for a robot control ...
- 6,632
8
votes
Accepted
Cartesian Velocity Control between Two 3D Poses
You essentially want to find the time derivative of a linear interpolation between two rotations. The easiest way to obtain this would probably to convert the rotation matrix between the two ...
- 941
7
votes
Accepted
Is the geometric inverse problem's solution "continuous" for a redundant robot?
I don't know if there is a formal proof to this, but in general, no the set of all possible joint configurations that correspond to a particular end-effector pose is not continuous. I think of the ...
Ben♦
- 5,780
7
votes
What is the learning (control) algorithm inside Cubli?
You should start by reading their academic papers:
M. Muehlebach, G. Mohanarajah, and R. D'Andrea, Nonlinear Analysis and Control of a Reaction Wheel-based 3D Inverted Pendulum, in Proc. Conference ...
Ben♦
- 5,780
7
votes
Explanation of Quadcopter Dynamics, Components and Control
A couple things, the first is that the controller does not really care what the "real" values are. Everything is relative, if the controller sees that it is sinking it will increase the thrust until ...
- 1,909
7
votes
Accepted
PID control: zero out integral on error sign change?
Generally, in a well-tuned PID, most of the job is done by the P term, which is responsible for driving PV to SP. Then, D and I serve as corrections: the D term regulates the profile as of how we ...
- 3,985
7
votes
Control VS artificial intelligence?
I think, it is easier to explain these areas in terms of guidance, navigation and control layers for an autonomous robot. Let's stay an autonomous robot is commanded to reach a desired goal position ...
- 367
6
votes
Accepted
Relation between pole placement and marginal stability?
You are most likely running into problems with the maximum time step in your simulation. This phenomenon is known as stiffness, where your equations of motion are highly sensitive to the size of the ...
- 1,377
6
votes
What's the difference between feedback and feedforward control?
It is arguable what is called reactive and what is not... however what is measured by sensors and what information the controller possesses is not arguable.
In feedback control, the system's outputs ...
- 6,632
6
votes
Robot never goes straight
Since the open-closed loop issue is already mentioned, I will give a comment to the "I once tried to run a dc-motor without a load".
Yes you might damage your motor with this but you can also damage ...
- 1,657
6
votes
Accepted
How can I apply different control approach without having a state space model?
Many control strategegies (PID is not neceserily one of these) are computing some of their parameters from your system. If you do not want to model your system yourself (or play around with it until ...
- 6,632
Only top scored, non community-wiki answers of a minimum length are eligible