Pedal and torque sensor tuning

This article concerns Pedal cadence and Pedal torque sensors. This article does not concern Axle torque sensors. Pedal torque sensors include both a cadence and torque signal and both parts must be tuned accordingly. Axle torque sensors do not include a cadence signal.

Pedal Cadence Sensor Tuning

The pedal speed sensor parameters that have the largest effect in terms of changing bike feel are the Pedalec positive motoring torque and Pedalec negative motoring torque ramps, and the Pedal speed map end and Pedal speed map offset.

Bike feel can be softened by increasing the Pedal speed map end and Pedalec positive motoring torque ramp values from their default values, 64 RPM and 200 ms respectively. Conversely, bike feel can be stiffened by decreasing these values.

Pedal sense delay represents the number of PFS input pulses that must be observed before the pedals are deemed active. Increasing this increases the amount the pedals must rotate before assistance is provided and Pedalec positive motoring torque ramp begins. Setting this too low might make the system too sensitive.

Pedal speed map end dictates the pedal rpm above which the pedal speed gain, the pedal assist request, is 100%.

Pedal speed map offset is the pedal-assist request when pedal rpm is zero, and pedals are active. Setting this above 0 gives you pedal-assist when at 0rpm, and setting this below 0 will require the pedal rpm to be greater than 0rpm before assistance is provided. The pedal-assist request is limited to between 0 and 100%. Note that if Pedal speed map offset is set greater than 1, the pedal-assist request will be 0% when above the Pedal speed map end.

Assist cut out distance is used to calculate the time (pedalec_timeout_delay) until the Pedalec negative motoring torque ramp begins based on the instantaneous vehicle speed and the time since the last pedal pulse. However, two bounds apply: The Pedalec minimum timeout is the minimum time before the negative ramp begins. The Pedalec maximum timeout is the maximum time before the negative ramp begins

In the absence of a pedal torque signal, the vehicle torque and speed behaviour is controlled using Assist Level Configuration.

Torque Sensor Tuning

As pedal-torque sensors include cadence, do not forget to tune the cadence sensor. See above.

The average pedal torque multiplied by the Pedalec power gain and the average pedal speed results in the average pedal speed gain before rate-limiting.

Pedalec torque symmetry is used to average the pedal torque input for calculating the average pedal torque. If set to:

  • 0 / One cycle averages the torque over one full pedal rotation. This provides the smoothest response, as it averages the torque input over the longest time. This option is best for single-sided torque sensors.
  • 1 / Half cycle averages torque over every half-pedal rotation.
  • 2 / Quarter cycle averages torque over every quarter pedal rotation.
  • 3 / Instantaneous, the pedal torque is not filtered and provides the instantaneous power output 1:1 to torque input. The feeling is similar to using a throttle.

Pedalec power gain can be considered the master parameter that allows the simplest adjustment of the feel of torque sensor-based bikes. Increasing Pedalec power gain will result in brisker arrival of the motor assist, whereas reducing it will soften the power delivery. Pedalec power gain multiplies the applied pedal torque relative to 64Nm to determine the average pedal torque that equates to a torque assist request of up to 100%. When Pedalec power gain is set to 1, we are setting full torque-assist request at 64Nm measured, when Pedalec power gain is set to 2, we are setting full torque-assist request at 32Nm, and when set to 0.5, we are setting full torque-assist request at 128Nm, from the Torque sensor offset plus the required Pedalec deadband torque voltage.

Torque assist request [%] = 100 [%] * Average pedal torque [Nm] * Pedalec power gain / 64 [Nm]

Pedalec deadband torque defines the amount of torque input, or noise input, that is needed before assistance is provided. For example, if you set the Torque sensor gain to 32Nm/Volt, and the Pedalec deadband torque to 10Nm. It will require the torque sensor voltage to climb 0.3125V (= 10Nm/(32Nm/Volt))) before providing assistance. Reducing this value will require less force before assistance is provided, but reducing too much may result in noise-induced jumpiness of the bike.

Pedalec initial torque dictates the initial power commanded when you begin pedalling and can be used to offset the lack of measured torque on one leg of some torque sensors. It is recommended to start tuning the torque sensor with Pedalec initial torque set to 0. Increasing this value increases the initial gain. The initial torque decays by half every 1 ms.

Pedalec positive motoring torque and Pedalec negative motoring torque ramps can also be adjusted.

Dynamic Pedal Gain

For 6.019+, you can set a dynamic pedal gain to dynamically adjust the pedal torque power gain with speed. This meets JISD9115 if set correctly, see below.

The controller calculates the torque request from the pedal input and uses Pedalec power gain to command motor assistance. The dynamic pedal gain feature allows for pedal gain to vary with speed.

This feature can be enabled/disabled by Features3 bit 1 Enable Dynamic Pedalec gain.  There are 4 parameters to configure this feature:

  • Vehicle Maximum Speed for Pedalec Assistance
  • Full Pedalec Assistance Speed for Pedal Torque gain
  • Maximum Pedalec Assistance Gain for Pedal torque
  • Minimum Pedalec Assistance Gain for Pedal torque

With this feature enabled:  

  • The controller will make sure to limit the Pedalec power gain at or under Maximum Pedalec Assistance Gain for Pedal torque if the vehicle speed is under Full Pedalec Assistance Speed for Pedal Torque gain
  • The controller will make sure the pedalec gain is equal to Minimum Pedalec Assistance gain for Pedal torque when the speed is equal to Vehicle Maximum Speed for Pedalec Assistance or higher  
  • Between Full Pedalec Assistance Speed for Pedal Torque gain and Vehicle Maximum Speed for Pedalec Assistance , BAC will make sure that the pedalec power gain is limited by the linearly interpolated gain between Maximum Pedalec Assistance Gain for Pedal torque and Minimum Pedalec Assistance Gain for Pedal torque

For JISD9115, set the values as follows:

  • Pedalec pedal gain = 2 G
  • Vehicle Maximum Speed for Pedalec Assistance = 24 km/h 
  • Full Pedalec Assistance Speed for Pedal Torque gain = 10 km/h 
  • Maximum Pedalec Assistance Gain for Pedal torque = 2 G 
  • Minimum Pedalec Assistance Gain for Pedal torque = 0 G 

Configuration Parameters

Pedal sensor tuning


Torque sensor tuning

Name DescriptionUnitsAddress

Dynamic pedal gain


Smart, Silent, Smooth.

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