Query on implementation of sport mode

ArduCopter Copter 3.1
1

First post here, so I hope I get this right.

I downloaded the latest version as of today (24th March) from GitHub, so I assume it’s version 3.1 (not sure where to look in the code for the version number to check). I was looking at control_sport.pde, and came across this section (lines 30-55):

[code]
// get pilot’s desired roll and pitch rates

// calculate rate requests
target_roll_rate = g.rc_1.control_in * g.acro_rp_p;
target_pitch_rate = g.rc_2.control_in * g.acro_rp_p;

int32_t roll_angle = wrap_180_cd(ahrs.roll_sensor);
target_roll_rate = -constrain_int32(roll_angle, -ACRO_LEVEL_MAX_ANGLE, ACRO_LEVEL_MAX_ANGLE) * g.acro_balance_roll;

// Calculate trainer mode earth frame rate command for pitch
int32_t pitch_angle = wrap_180_cd(ahrs.pitch_sensor);
target_pitch_rate = -constrain_int32(pitch_angle, -ACRO_LEVEL_MAX_ANGLE, ACRO_LEVEL_MAX_ANGLE) * g.acro_balance_pitch;


if (roll_angle > aparm.angle_max){
    target_roll_rate -=  g.acro_rp_p*(roll_angle-aparm.angle_max);
}else if (roll_angle < -aparm.angle_max) {
    target_roll_rate -=  g.acro_rp_p*(roll_angle+aparm.angle_max);
}

if (pitch_angle > aparm.angle_max){
    target_pitch_rate -=  g.acro_rp_p*(pitch_angle-aparm.angle_max);
}else if (pitch_angle < -aparm.angle_max) {
    target_pitch_rate -=  g.acro_rp_p*(pitch_angle+aparm.angle_max);
}[/code]

As I understand it, we first get the desired roll and pitch rates from the pilot commands, but then what I don’t get is that in the next lines, we immediately replace them by angles read from sensors.

I believe in sport mode, we interpret the stick input as a rate, so I don’t understand the lines

[code] target_roll_rate = -constrain_int32(roll_angle, -ACRO_LEVEL_MAX_ANGLE, ACRO_LEVEL_MAX_ANGLE) * g.acro_balance_roll;

target_pitch_rate = -constrain_int32(pitch_angle, -ACRO_LEVEL_MAX_ANGLE, ACRO_LEVEL_MAX_ANGLE) * g.acro_balance_pitch;[/code]

Any insight gratefully received.

2

You really need Leonard to comment on this as it’s his code. I have trouble understanding that part myself, though I understand most of the rest of the dynamics code (and wrote some of it). But that part… I can’t follow.

3

Thanks, hopefully he might notice this post. Basically I’ve built a quad from kit frame and some other parts and am coding a controller on an arduino Mega 2560. I know it would be easiest just to use your software as it is, but for me the process of bolting the sensor/dynamics/control code together is the fun learning part. However I know it would be madness to start from scratch, so I thought I’d scour the existing open source material to learn how its done. Sport mode looked like it would give something flyable by a noob, hence my interest in this section.

4

Hi Twistor,

To stop the copter from leveling in Sport Mode you need to reduce Acro_Balance_Roll and Pitch to zero. This then remove the auto level.

For filming using Yaw to “drive” around I like to set roll to 0.25 and pitch to 0.

Hope this goes some way to explaining what is happening.

Let me know if you have any more questions.

5

Thanks, yes, makes perfect sense. I wasn’t considering the case of g.acro_balance_roll = 0.