The National Highway Traffic Safety Administration (NHTSA) has reopened its investigation into a potential design flaw in Tesla vehicles, which may lead to sudden unintended acceleration. This comes after allegations were made that a voltage spike deep within the control systems could cause the vehicle to incorrectly read an accelerator input, even when none has occurred.
A Faulty Inverter at the Heart of the Issue?
The vehicle's inverter design is the center of these new allegations. The theory, put forward by researcher Dr. Ronald A. Belt, proposes that a flaw in the design could interpret a random voltage spike as a pedal application in rare instances. This is due to the Model 3's inverter using a single 1.65-volt calibration signal to monitor four ADCs (analog-to-digital converters, which convert the pedal position into an electric signal for the car).
When Voltage Spikes Trigger Unintended Acceleration
Under certain circumstances, such as slow driving, when the power steering requires more power, the draw on the 12-volt battery can cause a significant spike in the system. This voltage surge could lead the inverter to incorrectly conclude that the accelerator pedal has been pressed, resulting in unintended acceleration.
This unexpected acceleration could theoretically happen when a voltage spike, lasting only microseconds, occurs simultaneously as the car performs an ADC check, also lasting microseconds. Belt suggests that the frequency of these events aligns with the 200 or so incidents reported between 2013 and 2019.
The Silent Culprit
Adding complexity to this issue, Belt contends that due to the nature of the fault, it does not get logged as an error. The inverter’s misinterpretation of a voltage spike as a throttle input leaves no trace, leading to discrepancies between Tesla's vehicle data and owners' accounts, possibly explaining why the ODI initially denied the petition.
While Belt's allegations primarily focus on the Model 3, which features a unique inverter design, he notes that similar errors could occur in Model S and Model X vehicles. This opens up the potential for a broader scope in the ongoing investigation.
The NHTSA will now assess Belt's report to ascertain the validity of its findings. This isn't the first petition directed at NHTSA to investigate unintended acceleration in Tesla vehicles, but it presents a novel perspective, emphasizing a potential design flaw rather than a driver or software issue.
