The quad topples to the same side before it takes off. Now im wondering, why is that? if I'm understanding this correctly, I just need to set all motors to the same power and get the CW and CWW spin correctly. Right now, it seems that all motors are same power but as I increase the power, it starts leaning right and just falls before it goes up. What could be the problem?
Quad Wont get off the Ground, Topples to The Side
- Thread starter vortix
- Start date
You'll need a flight controller that accounts for the quadcopter's relative position and acceleration. Are you using an arduino/radio and expecting that you only need to account for the motor's speed?
If you're using a flight controller, be sure that the motors are mapped properly and that the ESCs are plugged into the correct spots. You will also want to check that the CCW propellers are on the CCW motors and vice-versa.
If you're using a flight controller, be sure that the motors are mapped properly and that the ESCs are plugged into the correct spots. You will also want to check that the CCW propellers are on the CCW motors and vice-versa.
im using Bluetooth and Arduino and going to create all the code for flight. Correct me if im wrong but if the blades and the motors are mounted correctly, shouldn't the quad atleast be able to fly up and slowly drift? right now it cant even get off the ground. It leans too much to one side. Just to be clear, there isn't any code to stabilize yet but I was under the impression that it wont be needed to be able to at least fly straight up and down.
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You might get off the ground, but you probably won't be able to land. Any tiny imbalance that the quadcopter normally could compensate for is going to have a larger effect with no recovery.
Can you post a video of it flipping?
I will when I have the time but just incase:
My frame is 5.5 inches
my propellers are 5-inch
Amazon.com: 8 Pair Propellers GemFan 6045 Glass Fiber Nylon Propeller for QAV250 280 H250 Multirotor Quadcopter by Hobby-Ace: Toys & Games
Amazon.com: 8 Pair Propellers GemFan 6045 Glass Fiber Nylon Propeller for QAV250 280 H250 Multirotor Quadcopter by Hobby-Ace: Toys & Games
www.amazon.com
Motors are Brushless 2600Kv
does these things fit together? The propellers are less than half an inch away from each others. Feels like theres barely any room. Could this be the issue?
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wafflejock
Well-Known Member
Big props aren't going to be a problem except if they run into the frame or each other (or your motors don't have the torque to accelerate/decelerate them quickly). Typically a 5" quad means it uses 5" props (you have 6" here the 6045 means 6.0 inch diameter, 4.5 inch pitch) I personally use 5045 5.0 inch with 4.5 inch pitch.
Main issue here is likely that you are just sending equal speed signal to all the motors but this isn't resulting in equal thrust. Basically there are a few issues that will cause the thrust to need to come out differently really (needs stabilization) to work at all really. If you could have simultaneous start (all motors start exactly at the same time) and all exactly the same specs on the motors then you could in theory just apply the same speed to all of them and get the same thrust out with the same props (also assuming props are perfect and balanced). Since none of those perfections exist in reality you need to have stabilization in place to some degree for it to fly at all really, the motors will start at slightly different times (calibration of ESCs will help reduce the difference but there will still be different static friction different windings, different magents etc. etc. that lead to them not actually starting up or accelerating in sync completely). Since one prop/motor/esc combo is going to be faster and stronger than the rest it will automatically end up tipping the quad from one corner or another and to compensate you need to be reading what is level and adjust the throttle signals to each ESC accordingly in order to achieve any sort of stable flight (even just up and down).
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Edit additionally even if you had perfectly equal thrust you'd need the quad itself to be perfectly balanced; center of gravity (CG) right at center of quad and thrust at center of quad if you have thrust away from CG the quad will pivot around the CG.
Some interesting stuff about how quads balance in video form here too, Tom Stanton does a lot of informative projects some involving quads:
Main issue here is likely that you are just sending equal speed signal to all the motors but this isn't resulting in equal thrust. Basically there are a few issues that will cause the thrust to need to come out differently really (needs stabilization) to work at all really. If you could have simultaneous start (all motors start exactly at the same time) and all exactly the same specs on the motors then you could in theory just apply the same speed to all of them and get the same thrust out with the same props (also assuming props are perfect and balanced). Since none of those perfections exist in reality you need to have stabilization in place to some degree for it to fly at all really, the motors will start at slightly different times (calibration of ESCs will help reduce the difference but there will still be different static friction different windings, different magents etc. etc. that lead to them not actually starting up or accelerating in sync completely). Since one prop/motor/esc combo is going to be faster and stronger than the rest it will automatically end up tipping the quad from one corner or another and to compensate you need to be reading what is level and adjust the throttle signals to each ESC accordingly in order to achieve any sort of stable flight (even just up and down).
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Edit additionally even if you had perfectly equal thrust you'd need the quad itself to be perfectly balanced; center of gravity (CG) right at center of quad and thrust at center of quad if you have thrust away from CG the quad will pivot around the CG.
Some interesting stuff about how quads balance in video form here too, Tom Stanton does a lot of informative projects some involving quads:
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wafflejock
Well-Known Member
Sorry to keep adding on to this but in order to achieve stable flight without major oscillations betaflight uses a set of parameters called Proportional Integral Differential or PID for calculating the actual thrust values that will be sent to the motors.
I haven't dug into the code for this but can explain in rough terms how the stabilization there works.
The receiver input is used to calculate the target orientation (or angle in angle mode), once the current and target orientation are known the PID values are used along with a short window of previous known orientations in order to adjust the thrust values.
The P value (proportional) is used to adjust how much the thrust will be adjusted based on the error or difference between the current and target orientation (basically proportional, so bigger the error bigger the change needed to correct the error and get to the target position), a P value that is too high results in overshooting the target, a low P value results in unresponsive behavior (it doesn't ever get to the target because the throttle changes it is making are too small).
The I value (integral) is used to adjust how much the thrust will be adjusted based on the window of changes from the past, basically this is compensating for how the quad is already moving due to previous thrust values and environmental factors like wind.
The D value (derivative) uses the derivative or instantaneous error value to correct for the current moment (looking into the future essentially if we are currently increasing the error or decreasing the error), the D factor multiplies the effect of the derivative error on the overall throttle.
For more details on this can read up here:
You don't necessarily need to use PID as the mechanism for calculating the thrust values but can say for sure it works in betaflight and know it is used generally for heating/cooling and other engineering tasks (where hitting some setpoint without constantly overshooting is needed, my 3d printer also uses this for the heaters).
I haven't dug into the code for this but can explain in rough terms how the stabilization there works.
The receiver input is used to calculate the target orientation (or angle in angle mode), once the current and target orientation are known the PID values are used along with a short window of previous known orientations in order to adjust the thrust values.
The P value (proportional) is used to adjust how much the thrust will be adjusted based on the error or difference between the current and target orientation (basically proportional, so bigger the error bigger the change needed to correct the error and get to the target position), a P value that is too high results in overshooting the target, a low P value results in unresponsive behavior (it doesn't ever get to the target because the throttle changes it is making are too small).
The I value (integral) is used to adjust how much the thrust will be adjusted based on the window of changes from the past, basically this is compensating for how the quad is already moving due to previous thrust values and environmental factors like wind.
The D value (derivative) uses the derivative or instantaneous error value to correct for the current moment (looking into the future essentially if we are currently increasing the error or decreasing the error), the D factor multiplies the effect of the derivative error on the overall throttle.
For more details on this can read up here:
PID Controller : Working, Types, Advantages & Its Applications
This Article Discusses What is a PID Controller (Proportional Integral Derivative), History, Block Diagam, Types & Its Applications
www.elprocus.com
GitHub - betaflight/betaflight: Open Source Flight Controller Firmware
Open Source Flight Controller Firmware. Contribute to betaflight/betaflight development by creating an account on GitHub.
github.com
You don't necessarily need to use PID as the mechanism for calculating the thrust values but can say for sure it works in betaflight and know it is used generally for heating/cooling and other engineering tasks (where hitting some setpoint without constantly overshooting is needed, my 3d printer also uses this for the heaters).
Thank you. how do I know if my thrust is on the center of gravity? I just bought a premade frame so I assumed that's already taken care off. Also, I have an accelerometer attached to the quad, would that be enough to keep it level if I use it? or I should I be looking for something else?
right now, im thinking that since I have an accelerometer, I can read its initial state while the quad is off and then constantly Read its changes as I increase motor speed. Then, read the difference between the previous accelerometer reading and its current reading and change the motor speed towards that Initial position. Would that work ?
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wafflejock
Well-Known Member
Roughly this is what betaflight is doing in angle mode but typically the flight controllers use I think an MPU6000 or similar IC with accelerometers+gyro (I bought one here to play with that also includes barometer which can be useful for attempting some sort of altitude hold) https://www.amazon.com/gp/aw/d/B01I1J0Z7Y/ref=ppx_yo_mob_b_inactive_ship_o0_img?ie=UTF8&psc=1, might work for you). The gyros give relative orientation changes but accelerometer might be enough to attempt just level flight, I believe betaflight uses the gyros to get a picture of how the angle is changing over time for use with the PID loop and targets the level (initial position or calibrated position) of the accelerometer.
wafflejock
Well-Known Member
Regarding the center of mass the quad frame motors and ESCs might have CG roughly in middle of the craft but usually few hundred grams of weight in battery that is difficult to perfectly center and keep it there. Typically either the front or the back motors are pushing a bit harder just to compensate for the off center weight (really just adjusting to the angle tipping out of balance moreso than directly accounting for the weight)
wafflejock
Well-Known Member
I am a computer scientist hence the lengthy nerdy posts 
but dugdog put it succinctly.
I also think without the fast fairly accurate feedback you can get from gyros hitting any sort of stable flight with accelerometer alone will at best be a wobbly scary flight (wright brothers style).
Definitely be cautious with these props/motors they can get to speeds that will slice flesh like a hot knife through butter. No need to end up in ER for a school project.
but dugdog put it succinctly.I also think without the fast fairly accurate feedback you can get from gyros hitting any sort of stable flight with accelerometer alone will at best be a wobbly scary flight (wright brothers style).
Definitely be cautious with these props/motors they can get to speeds that will slice flesh like a hot knife through butter. No need to end up in ER for a school project.
Dugdog47
Well-Known Member
Yeah I didn't get much schoolin when I was young but I did watch the history of helicopters which I used to be fascinated with. Did you know the first quadcopter was invented in 1920?
Btw vortix be warned that the motors and props combination you are using is potentially very dangerous, we nick-named quads "face blenders" for a reason lol.
Btw vortix be warned that the motors and props combination you are using is potentially very dangerous, we nick-named quads "face blenders" for a reason lol.
wafflejock
Well-Known Member
First off agree doing this on a 5" build is super sketchy. Since you aren't sure what's going to happen with it while testing/debugging and are likely to have crashes you are really better off doing a 3" build, it's less dangerous and less likely to destroy itself. If you can return the frame and get your electronics to fit onto a 3" frame (might be ugly, but can work) you'd be a lot safer experimenting without me worrying I'm leading you to your death.
Didn't know about the first one in 1920, but that does happen often where someone builds an early attempt, but the technology available isn't really viable or cheap enough to make it accessible to us "normal" (not insanely wealthy) people. I know electric cars have been a thing a few times I believe even before internal combustion engine cars started rolling off the line at Ford but yah no high capacity lithium ion cells at the time or charger network (or stable electricity for that matter).
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Alternative could keep the 5" setup for regular flying with a known good FC and additionally pick up a small 3" one (I have the kingkong 90gt, know the mobula7 is supposedly very good option now too)
Didn't know about the first one in 1920, but that does happen often where someone builds an early attempt, but the technology available isn't really viable or cheap enough to make it accessible to us "normal" (not insanely wealthy) people. I know electric cars have been a thing a few times I believe even before internal combustion engine cars started rolling off the line at Ford but yah no high capacity lithium ion cells at the time or charger network (or stable electricity for that matter).
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Alternative could keep the 5" setup for regular flying with a known good FC and additionally pick up a small 3" one (I have the kingkong 90gt, know the mobula7 is supposedly very good option now too)
I Agree, My plan from the beginning is to create a tiny quad that sits in the palm of your hand. But since im a noob, I already purchased these motors and frame not realizing their strength. Right now, I don't think I can return them since I shortened the wire quite a bit. Honestly, I admit that I almost got hit right on the face because I increased the speed instead of decrease it by mistake. Either way, don't have the finance to buy tools for a new frame and motors etc.. I guess ill have to wait for now :[.
while we are On topic, I happen to have these :
Amazon.com: Stemedu 5PCS GY-521 MPU-6050 Accelerometer Gyro Sensor 6DOF 3-Axis IMU 16 Bit AD Converter Data Output IIC I2C for Quadcopter Drone RC, 40P Dupont Cable: Home Audio & Theater
Amazon.com: Stemedu 5PCS GY-521 MPU-6050 Accelerometer Gyro Sensor 6DOF 3-Axis IMU 16 Bit AD Converter Data Output IIC I2C for Quadcopter Drone RC, 40P Dupont Cable: Home Audio & Theater
www.amazon.com
Amazon.com : WINGONEER MMA7361 Accelerometer Sensor Acceleration Module Angle Inclination Sensor : Electronics
Amazon.com : WINGONEER MMA7361 Accelerometer Sensor Acceleration Module Angle Inclination Sensor : Electronics
www.amazon.com
Problem is, I tried to get any kind of feed back from them that makes sense to me that I can use to create stable flight and I failed. I'm completely lost on how to communicate with these or how to really use them. Don't even know how to hook them up to the Arduino. Im aware of the provided schematic in the page but I hooked it up like that but seems that something is off.
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What does fcb stand for?
wafflejock
Well-Known Member
@vortix you'll need to use I2C protocol like they show in a few of the images. Looks like there is a nice lib here for using I2C and had lots of devices included including the mpu6050 so should simplify getting the data out in a formatted way that make some more sense. That said I don't believe I've ever used the gyros on mine directly yet either so can't guide you much there. The lib that looks relatively easy to use is here:
Many libraries in arduino you can find by using the manage libraries menu option and searching, but can also check out the usage above, generally can download an arduino library zip and just unzip it into the libraries folder for your install.
GitHub - jrowberg/i2cdevlib: I2C device library collection for AVR/Arduino or other C++-based MCUs
I2C device library collection for AVR/Arduino or other C++-based MCUs - jrowberg/i2cdevlib
github.com
i2cdevlib/Arduino/MPU6050 at master · jrowberg/i2cdevlib
I2C device library collection for AVR/Arduino or other C++-based MCUs - jrowberg/i2cdevlib
github.com
Many libraries in arduino you can find by using the manage libraries menu option and searching, but can also check out the usage above, generally can download an arduino library zip and just unzip it into the libraries folder for your install.