Mechanical System

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The Fraunhofer IESE ConceptCar

The base platform of the Concept Car is a RC Car Model CE-5 from Carson Modellbau. This platform has the following parameters:

  • Scale is 1:5
  • Dimensions (l*w*h) are 80cm * 40cm * 23 cm
  • Weight is ~ 8.4kg
  • Top speed is ~60km/h
  • Rubber wheels, 12cm in diameter
  • Gear reduction from motor shaft to rear wheels is 20:44 * 20:77 (2 transmissions)
  • Differential gear


Engine

The Concept Car engine is based on an air-cooled sensorless brushless electrical motor, which is presented in Figure 1.1.

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Figure 1.1. Basic Description of the Concept Car Engine

Each part of the engine presented in Figure 1.1 is described in the following:

  • The motor is a 1930/9 from Lehner Motoren and its characteristics are shown in Figure 1.2 [LM09].
  • The engine control is a Power JAZZ from Kontronik. Its characteristics are presented in Table 1.1 [Kon09].
  • The power is supplied by an accumulator with a nominal voltage of ~21V and the ability to sustain a permanent discharge current of at least 80A. The actual type and internal construction of the accumulator is irrelevant, as long as these specifications are met. Currently a 5S1 LiPo accumulator is used.
  • The battery can be cut off from the engine controller with an emergency switch (200A)
  • The 5-6V supply voltage of the steering servo (max. 3A) is generated by a high-efficiency step-down voltage converter.
The engine control and the emergency switch
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Figure 1.2. Motor Characteristics

Due to its sensorless nature, the engine tends to stutter when the car is pulling off.

Table 1.1: Kontronik Power JAZZ characteristics
POWER JAZZ 63V Characteristics (in English)
18-45 Cell count (NiCd/NiMH)
5-15 Cell count (LiPo)
13-63 Operating Voltage (V)
120 Contin. current (A) (2,4Ah battery)
200 Max. current (A) (15sec)
84 Size (mm) length
51 width
35 height
220 Weight (g) with cables
4/6 Cable-cross-section (mm²)
/ BEC
x Auto Programming Mode
x ProcCARD ability
x Automatic Power Consumption APC
x EMF brake can be disabled
/ Proportional brake
x Reverse polarity protection
x Short circuit protection
x False start protection
x Current limiting
x Overtemp. protection
x Undervoltage cutoff
x -"- can be disabled
x Slow down instead of cutoff*
x Active free wheeling circuit
8-32 PWM frequency (kHz)
1.9 Total copper thickness
x Reverse rotation direction

Radio Control

The ConceptCar is remotely operated via a standard 2 channel 27MHz radio transmitter system. The channels are used for throttle and steering data. The radio receiver generates a 50Hz PWM signal with 5% to 10% duty cycle.

Steering System

The steering system has simple mechanics; a servo motor sets the steering angle. Within a range of ±30° the steering angle is set to (pulse – 1.5ms) * 1° / 0.018ms, where “pulse” denotes the length of a PWM pulse at a PWM frequency of 50Hz.

Brakes

The ConceptCar's hydraulic brakes

The ConceptCar features a set of hydraulic brakes on the front wheels. At the current state, they can not be triggered separately, but the electrical system is already prepared for that.