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BSG System

Dynamic system analysis of a BSG

A Belt Starter Generator (BSG) system is a type of mild hybrid technology used in automobiles.

The BSG combines the functions of a starter motor and a generator (alternator) into a single unit. It is typically connected to the engine via a Poly-V Belt

BSG systems are engineered to address several critical functions in modern vehicles:


Engine Starting: Ensures reliable and efficient starting of the vehicle's engine.

Boosting: Provides additional power to the engine when needed.

Energy Recuperation: Harnesses and reuses energy typically lost during braking or deceleration.

Partial Support During Driving: Offers auxiliary power to the engine during regular driving conditions, enhancing overall vehicle performance.

Our Expertise in Belt Starter Generator Systems

inculde wide range of capabilities:


Simulation of dynamic belt drives, crankshafts, and electric motors.

Analysis of electrical excitation and the functioning of electrical components.


Our Engineering Approach:
Our methodology involves an integrated system simulation that includes the belt drive, crankshaft, electric motor, and tensioning system. This approach allows for the comprehensive design and optimization of each technical component while considering their interactions. We focus on investigating potential issues in different components.


FEAD: dynamic span forces, belt flapping, loss of contact between the belt and pulley, and stick-slip behavior of belt pulley contact, belt powerloss

Tensioning Systems: Damping characteristics, forces in tensioner components, wear in bushing elements.


Generator/Electric Motor: Bearing forces in the electric motor and controller parameter optimization.

By addressing these specific aspects, we ensure that each component of the BSG system operates at its peak, leading to a more efficient and reliable vehicle performance.

Engine Start Optimization - Initial

Electrical and mechanical system analysis of combustion engine start. Generator torque (motor mode) is ramped in until full load curve is reached.

After reaching target speed generator torque is reduced.

Identified problems:

  • Example shows high hub load level at generator pulley


  • Start strategy can be easily modified with connected electrical system

Optimization Steps:

  • Generator torque (motor mode) is ramped in until full load curve is reached

  • With help of electrical machine model the torque curve is modified during start. Torque signal follows 5kW function instead of full load curve

  • Hub load level is reduced with adapted start procedure

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