Longitudinal Control: ACC
Longitudinal control, or addaptive cruise control (ACC), is the capability to accelerate and slow down the car based on traffic, user max speed settings and map information integration (curvature, traffic, etc). This is an ongoing effort. These pre-AP cars lack electronic pedal control for (acceleration and braking) and radar.
As of 2019 we have both software-only and hardware-based Adaptive Cruise Control.
The easiest setup is to use the vision only "mock" radar in OpenPilot. It works OK on highway if there are not many speed changes. The radar accuracy has improved since 0.5.11 but still has a 1-2 seconds delay vs real time. Also, it only tracks one car, the lead car. In order to use this for longitudinal control, we use CAN messages to create fake cruise stalk messages, increasing/decreasin the speed by 1 (half action) or 5 (full action). This creates the desired outcome but the speed changes are not very smooth. Also, the Tesla CC (and thus OP ACC using cruise stalk spamming) only works above 18 MPH (29 km/h).
The next step up is to replace the CC stalk spamming with a pedal interceptor. This allows speed control from 1 MPH (1.6 km/h) but you need to keep in mind that regenerative braking only works above 5 MPH (8 km/h). The cost of this updgrade is about $100.00 USD.
Next upgrade would be to add a Tesla Bosch Radar. This increases the cars/objects tracked from 1 to 32 and allows real time monitoring of distance and relative speed for lead car and cars on the side lanes, increasing the smoothness and precision of the ACC. This is still limitted in braking power. If you have IC/CID integration, this feature shows up to 6 cars on the IC. The cost of this upgrade is about $500.00 USD and requires some extensive work (including removing and re-installing the front bumper).
Final upgrade for ACC in order to obtaing full stop and go capabilities is to replace your old vacuum based braking system with an electronic braking system (iBooster). This code is in development as of May 2019. The cost for this upgrade is about $6-700.00 USD and requires root access and knowledge on how to flush your brake lines. This feature will give you full stop-n-go capability.
