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Questions tagged [stability]

the state or quality of being stable.

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0answers
15 views

Hover control for quadcopter doubt?

For my project I need to make a hover control using state space approach for a quadcopter. So far I have taken a non linear state space model from a research paper that used 12 states, 4 inputs and ...
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0answers
63 views

Stability of dynamical system via Lyapunov

I have a dynamical system which has the following form: $\dot x=\mathcal F_1(m_1)x+\mathcal F_2(m_2)x$. My objective is to find the parameters $m_1$ and $m_2$ via LMI (linear matrix inequality) using ...
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1answer
58 views

stable altitude quadcopter

I'm currently working on a project to generate a stable altitude and automatic control for a quadcopter I'm using arduino as the flight controller Ultrasonic sensor HC-SR04 MPU-6050 However my ...
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0answers
11 views

Gyro-stabilize cargo in VTOL UAV configuration

How would you go designing a "gimball" lets say mechanism which would keep the cargo of a VTOL UAV at the same configuration as placed in it before liftoff? Lets say not trying to spill a glass of ...
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0answers
36 views

how to make a robot stand after it has fallen [closed]

I have seen the methods to make a bipedal robot stand and walk keeping its center of gravity in stable mode, but how can i make the robot stand if it falls in ground? For example right now i'm using ...
4
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1answer
148 views

Comparison of Balance Bot design

I'm planning to build a Balance Bot and I would like to know which design should I go with. There's a vertical design such as the ArduRoller and on the other hand, there's the typical stacked type of ...
11
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4answers
312 views

Why is it so hard to walk?

At least, on two legs. Asimo, one of the best known humanoid robots, is already capable to walk, although it doesn't seem to do this very stable. And it is a recent result. As far I know, the legs ...
2
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1answer
86 views

PID Gains: Drop in control loop rate, need to retune?

Good Day, I am working on an autonomous quadcopter. May I ask if there is a significant difference if my control loop dropped from 500Hz to 460Hz due to added lines of code that would require ...
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1answer
366 views

Using Quaternions to feed a quadcopter PID stabilizing controller to avoid Gimbal lock

I am trying to control my F450 dji quadcopter using a PID controller. From my IMU, I am getting the quaternions, then I convert them to Euler's angles, this is causing me to have the Gimbal lock issue....
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1answer
26 views

Locking the yaw direction of a laser pointer

I have a laser pointer on a handle grip and I'm trying to keep the laser pointer's yaw direction, which can rotate at around 10deg/s. So I have the laser pointer on a stepper motor and an ...
0
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1answer
517 views

Quadcopter: X-Y Velocity PID Controller

Good day, Introduction I am currently working on an autonomous quadcopter project. I have currently implemented a cascaded PID controller consisting of two loops. The inner rate loop takes the ...
4
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1answer
407 views

Quadcopter refuses to fly when the Yaw PID component is added

Good day, I would like to ask why is it that when I add the Yaw control to my PID controller for each motor. The quadcopter refuses to take off or maintain its altitude. I am curently using a ...
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2answers
94 views

Fixed Wing UAV: Do inherently unstable systems desire to be stable for all cases when a closed loop control is implemented on them?

As we all know fixed wing vehicles are designed to have inherent instability which is what enables all fixed wing vehicles to fly. However does this apply to all cases? Do inherently unstable ...
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1answer
835 views

Quadcopter PID Tuning for Altitude Hold/Position Hold along Z axis

Good day, I have just finished tuning the Pitch and Roll PID's. I did this by setting the throttle such that the quad is weightless. I did the tuning of each axes separately. I would just like to ask ...
1
vote
1answer
134 views

Ultrasonic Sensor's Lag (20Hz) effect on PID contol loop rate (150Hz)

Good day, I would like to ask how is it possible to use an ultrasonic sensor for altitude hold in a quadcopter if the sampling rate of the Ultrasonic sensor (HC-SR04) is only 20Hz before incurring any ...
1
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1answer
481 views

Quadcopter PID: Controller is Saturating

Good day, I am currently creating an autonomous quadcopter using a cascading PID controller specifically a P-PID controller using angle as setpoints for the outer loop and angular velocities for the ...
0
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1answer
84 views

Helicopter Stabilization Algorithm

I've hacked a rc helicopter, and I am able to control it by running a program on my computer. I am interested in writing algorithms that will stabilize the helicopter. For instance, the helicopter is ...
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2answers
1k views

PID Control: Integral error does not converge to zero

Good day, I had been recently reading up more on PID controllers and stumbled upon something called integral wind up. I am currently working on an autonomous quadcopter concentrating at the moment on ...
2
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1answer
472 views

Quadcopter PID Controller: Derivative on Measurement / Removing the Derivative Kick

Good day, I am currently implementing a single loop PID controller using angle setpoints as inputs. I was trying out a different approach for the D part of the PID controller. What bought this ...
4
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2answers
3k views

Quadcopter PID Control: Is it possible to stabilize a quadcopter considering only angle measurements?

Good day, I am a student currently working on an autonomous quadcopter project, specifically the stabilization part as of now. I am using a tuned propeller system and I also already considered the ...
2
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1answer
133 views

What is $\alpha \sin(\theta) + \beta \frac{d \theta}{d t}$ in the inverted pendulum problem?

I am preparing for an exam in neural networks. As an example for self-organizing maps they showed the inverted pendulum problem where you want to keep the pole vertical: Now the part which I don't ...
4
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1answer
115 views

Humanoid balancing

I'm currently working on Humanoid robot. I've solved the Forward & Inverse Kinematic relations of the robot, and they turn out to be fine. Now I want to move onto Walking. I've seen tons of ...
4
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1answer
109 views

Relation between pole placement and marginal stability?

I'm given an assignment in which I have to design a full state feedback controller by pole placement. The state space system is fully controllable and I've been using Matlab/Simulink to determine the ...
2
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2answers
195 views

Quadcopter stability vs (PID error signal lag and sample time)

The question I am asking is that, what is the effect on stability of increasing or decreasing both the sample time and lagging of error signal to PID. Does it helps in stability or degrade it?
3
votes
1answer
623 views

PID quaternion contoller

I want to control the attitude(roll, pitch, yaw) of a vehicle capable of pitching and rolling. To do this I have created a quaternion PID controller. First I take the current attitude of the vehicle ...
4
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1answer
1k views

Deciding length of quadcopter arms

How quadcopter's arm length affect stability? As per my view I'll have better control on copter with longer arms but with stresses in arms and also it doesn't affect lift capabilities.
8
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1answer
182 views

How do I decide the size of the time steps between sensing and control actuation?

My Background: My experience is in solid mechanics and FEA. So I have zero experience in robotics/controls. Problem Description I'm developing a control strategy to stabilize a complicated 6-...
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1answer
72 views

Building parts, and keeping laser alignment steady

I am building a laser gun for pentathlon targets (also doing one). I would like to know how build a part of the gun and if I can count on a steady laser if it is attached to a motor. The question is ...
3
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0answers
126 views

On-board monocular odometry for quadcopter stabilization

Has anyone done this with EKF/PID on a small microcontroller? Or know of code snippets to help implementing this?
1
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1answer
58 views

How can I know which system is easier to control using PID controller?

I have a inverted inertia wheel pendulum. I suppose that if I have a wheel with larger inertia at its top, the system would be more stable. How can I prove or disprove my conjecture?
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1answer
109 views

Step Motor and Bevel gear calibration

I am new to robotics. I want to understand how gears state is preserved as the gears turned to same positions repetitively. I have a bevel gear and a step motor connected to one gear. This gear will ...
8
votes
4answers
6k views

How to use quaternions to feed a PID quadcopter stabilization loop?

I'm making a quadcopter. I have set up a PID loop to stabilize it to a given Euler angle (pitch and roll). The problem arises when the roll approaches 90 degrees (45 degrees and up). The values don't ...
12
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3answers
18k views

Quadcopter PID tuning

In continuation of the question I asked here: Quadcopter instability with simple takeoff in autonomous mode ...I'd like to ask a few questions about implementing a basic PID for a quadrotor ...
2
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2answers
704 views

KK2.0 Quad Stablility

I'm running a kk2.0 + 4 20A Multistar ESCs + 4 EMax GF 2215-20 motors + 4 Slow Fly Props After about a foot off the ground, the entire quadcopter starts wobbling like crazy (no auto-level). Any ideas?...
5
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1answer
93 views

Guidance for compensating internal forces on closed loop chain

I'm working on a legged robot and generating joint torques. Basically the robot seems to be statically stable to some extend. The robot goes instable if the center of pressure moves to the border of ...
11
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3answers
13k views

How to stabilize a quadcopter

Today was my quadcopter's first "flight". I'm running megapirate on a Crius AIOP v2 with a Turnigy Talon v2 frame. I only touched the throttle stick on my remote, nothing else. When I felt the ...
20
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5answers
2k views

Is it better to have batteries distributed at the rotors or the center of the multicopter?

I've seen 3 approaches to mounting batteries on a multicopter: All the batteries rigidly mounted near the center of the airframe All the batteries in a bag hanging under the center of the airframe ...
20
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4answers
5k views

What frequency does my quadcopter output-sense-calculate-output update loop need to stay stable?

With a 600 mm (2 foot) motor-to-motor quadcopter, what frequency does my output-sense-calculate-output update loop need to stay stable? I'm estimating a total takeoff weight of very roughly 2 pounds (...
12
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2answers
816 views

Is it better to have weight distributed over the wheels or the center of the robot?

When designing a standard 4 or 6 wheel robot, is it better to have the weight distributed primarily in the center of the robot, or over the wheels, or is there no difference? Specifically, which ...
15
votes
4answers
306 views

Is it possible to both move and stabilize a two wheeled robot with no gyroscopes?

With two wheeled robot like this one, I have managed to stabilize it while keeping it stationary. This was done using a digital feedback control system by reading the position of the wheels to ...