kcevo Posted October 29, 2021 Report Share Posted October 29, 2021 Has anyone ever asked for the PID in boost control to be tables. Where boost error target was the x axis and then proportional, integral, and derivative gain can be adjusted based on the amount of error from target? Similar to the table below for proportional gain on a subaru oem ecu boost control strategy. Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 29, 2021 Report Share Posted October 29, 2021 Typically you only need a proportional table in control systems where there is no derivative action. They do this to ramp proportional out as you get close to target to reduce overshoot. Derivative effectively does the same thing, but does it better as it takes into account how fast you are approaching target. But the problem with derivative (the reason they probably dont use it) is it can make the control loop sensative to noise when you are sitting on target. Link gets around this by using PD control only on approach to target (Stage 2), then switching to PI control once close to target (stage 3). One of the other high-end ECU's I used to work with uses a variation of the proportional table, but it is a 3D table with error on one axis and rate of boost change on the other. This allows the rate you are approaching target to be taken into account but is a total ball ache to tune. Quote Link to comment Share on other sites More sharing options...
mike2016 Posted October 30, 2021 Report Share Posted October 30, 2021 Is it wiser to have stage 3 activate a bit sooner than what's in the help file, to stabilize the boost a bit sooner? i've been messing with boost control for a while, it seems no matter what setting i have in P/D, it would oscillate a bit until it reach stage 3 Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 30, 2021 Report Share Posted October 30, 2021 21 minutes ago, mike2016 said: Is it wiser to have stage 3 activate a bit sooner than what's in the help file, to stabilize the boost a bit sooner? No, because the whole idea is you want the D to "put the brakes on" and pull DC back just as you get close to target. If you switch to stage 3 early you will get what is known as integral windup which will add positive DC and cause a big overshoot. If is is oscilating you likely have too much P. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.