Case study of building a calibration room for heavy-duty trucks

The calibration of heavy trucks (referred to as "heavy-duty trucks") is significantly different from that of passenger cars. As a production tool, heavy trucks operate under high loads and harsh conditions (such as long-distance freight, mining transportation, and high-altitude climbing) for a long time. Therefore, their calibration focuses more on power, economy (fuel efficiency), reliability, high-pressure safety, and complex multi axis drive control.
With the transformation of heavy trucks towards new energy (pure electric, hydrogen fuel cell) and intelligence (advanced autonomous driving), the calibration process of heavy trucks has evolved from traditional fuel powertrain calibration to an extremely complex system engineering.

1. Classification of core calibration sections
The calibration of modern heavy-duty trucks is mainly divided into three core areas:
(1) Traditional powertrain calibration (fuel/natural gas)
① Engine calibration (ECU): fuel injection strategy, ignition advance angle, intake management, turbocharging control. Heavy trucks pay special attention to low-speed and high torque output calibration.
② Post processing calibration (DCU/SCR): Heavy trucks are extremely sensitive to environmental regulations (such as National VI B). The focus of calibration is on urea injection quantity and DPF (particulate filter) regeneration control, ensuring that emissions meet standards at various environmental temperatures without "speed limit or torque limit".
③ Automatic Transmission Calibration (TCU/AMT): AMT (Automatic Manual Transmission) is almost universally used in heavy-duty trucks. The calibration core is the shifting schedule, which requires automatic selection of the optimal gear based on the vehicle weight (unloaded 10 tons vs fully loaded 49 tons) and slope to prevent frequent gear jumps and clutch overheating.
(2) Calibration of new energy heavy-duty trucks (pure electric/hydrogen fuel cells)

① VCU (Vehicle Control Unit) calibration: torque management. The power of heavy-duty truck motors is high (often above 400kW), and calibration needs to prevent excessive torque during starting from causing tire slippage or transmission shaft breakage.
② BMS (Battery Management System) calibration: Heavy truck batteries have a large capacity (usually 280~600 kWh). The calibration focuses on high-power charging and discharging strategies, strong power battery feedback (braking energy recovery) during heavy load downhill, and thermal management.
③ FCU (Fuel Cell Controller) calibration: Water thermal management, hydrogen oxygen gas flow matching, and injector control of hydrogen fuel cell heavy-duty trucks to ensure system life under extreme cold/heavy load conditions.
(3) Intelligent driving perception and control calibration (ADAS/autonomous driving)
① External calibration of sensors: Heavy truck body length (long head/flat head, trailer), severe vibration, and rigid installation points of cameras and LiDAR are prone to small displacements, requiring high-frequency dynamic online calibration capability.
② Vehicle dynamics control calibration (chassis): Heavy trucks have extremely high mass inertia, long braking distance, and there is a risk of trailer tipping and overturning. The calibration of AEB (Automatic Emergency Braking) and ACC (Adaptive Cruise Control) must take parameters such as trailer mass, axle load distribution, and air brake response delay (usually several hundred milliseconds slower than hydraulic braking) as core inputs.

2. Standard Process for Calibration of Heavy Trucks
Both power calibration and vehicle calibration usually follow the V-model development process, which is mainly divided into four stages:
Phase 1: MIL/HIL simulation calibration (desktop phase)
Conceptual solution: Establish a physical model of the heavy-duty truck (including trailer dynamics model) in software such as Matlab/Simulink.
Hardware in the Loop (HIL): Connect the controller to the simulation bench and run the basic calibration algorithm in a virtual "high mountain, high cold, high temperature" environment, completing 60% to 70% of the basic data filling to ensure that the software has no fatal logic errors.
Phase 2: Bench Calibration (Laboratory Stage)
Engine/motor bench: Install the power source on the test bench, simulate the working conditions of heavy trucks under different loads through a dynamometer, perform steady-state and transient calibration, and outline the basic map (such as the engine universal characteristic economic zone).
New generation: Vehicle hub platform. Drive the entire heavy-duty truck onto a large roller platform, and the environmental chamber can simulate temperatures ranging from -40 ^ circ ext {C} to 50 ^ circ ext {C} for high-precision energy flow and emission calibration.
Phase 3: Calibration of the actual vehicle site (testing site stage)
Basic performance calibration: The vehicle is calibrated for starting, accelerating, shifting, and braking under different loads (empty, half load, full load) in a closed test field (such as regular roads, high loop roads, and comfort roads).
Special operating condition calibration: such as curved road and washboard road, used to test the intervention timing of heavy truck EBS (electronic brake system) and ESC (vehicle stability system).
Phase 4: Three high test and three line calibration (extreme environment stage)
This is the most difficult and critical step in the calibration of heavy trucks, which directly determines the reliability of heavy trucks in the real market.

3. The unique challenge of heavy truck calibration
(1) The load variable span is extremely large:
An empty heavy truck may only weigh 9 tons, but a compliant full load is 49 tons (some special loading conditions may even be heavier). The calibration algorithm must be able to accurately estimate the current weight and slope of the vehicle, otherwise if the AMT gearbox is mistakenly judged as unloaded and shifts into high gear during full load climbing, it will cause the entire vehicle to "stall" or even slide downhill.
(2) Time delay of air brake (pneumatic brake):
Passenger cars use hydraulic braking, and the response is almost instantaneous. Heavy trucks rely on air pressure transmission, with a physical delay of 0.2 to 0.5 seconds from the moment the brake pedal is pressed to the response of the rear axle and trailer brakes. When calibrating the AEB braking strategy of the intelligent driving system, the time of this "pneumatic pipeline" must be included as a hard compensation parameter.
(3) The uncertainty of trailers:
The calibration of the main vehicle (front end) is fixed, but the trailer towed behind may be empty, full, high center of gravity (container), or prone to shaking (liquid tanker). When calibrating the chassis control of intelligent heavy-duty trucks, it is necessary to introduce the "trailer recognition and adaptive algorithm" to prevent the main vehicle from losing control due to trailer swing.
Due to the fact that calibration directly determines the "fuel/electricity cost" and life safety of truck drivers, the calibration cycle of heavy trucks usually lasts for 1-2 years and requires actual road verification of tens of thousands of kilometers before final delivery for mass production (SOP).