Innovation driver for sustainable and future-oriented mobility
The E-Jet research vehicle is an innovative example of alternative mobility concepts for the future and was initially funded as a concept study by the Hans Hermann Voss-Foundation. In the conceptual space between pedal-driven vehicles and the classic passenger car, this project is creating an innovative vehicle for future-oriented mobility. As a "human-hybrid" vehicle with serial drive, it represents a sustainable mobility solution that is complemented by a future-oriented steering concept and exceptional aerodynamics. The combination of these key features characterizes this vehicle, which can also be regarded as a fitness device. The aim of further development is to demonstrate the subsystems in a way that can be experienced and evaluated, and at the same time to create an innovative vehicle for rural mobility.
In this context, the term "human-hybrid" describes a combination of an electric and a pedal drive, as can already be found in pedelecs today - but without a chain or toothed belt. What is special in this vehicle is that a drive topology and control system is presented that optionally magnifies the pedaling torque of the driver by several orders of magnitude. Thus, it is possible to create a symbiotic connection between the driver and the vehicle. On the one hand, the serial plug-in hybrid structure uses the driver's pedaling motion as a setpoint for the vehicle's longitudinal guidance, and on the other hand, electrical energy is fed into the drive system via the generator. This theoretically allows any range to be achieved, although the driving speed is limited by the driver´s power when the battery is empty.
Specifically, this means that the drive topology allows the vehicle to accelerate to speeds of up to 120 km/h by operating the crank mechanism. The available power of the vehicle is equivalent to 100 times the average power of a human being. Compared to existing vehicle concepts such as electrically assisted bicycles (pedelecs), the vehicle concept is characterized by an amplification factor that can be adjusted over a wide range. For this reason, an electromechanical decoupling of driver input and vehicle response is implemented (cycle-by-wire). The driver's request is determined by sensors and transmitted to the vehicle, and the vehicle response is returned to the driver as feedback.
The E-Jet research vehicle has a powertrain in which the driver contributes to the overall vehicle performance with his own power. A sophisticated insight into the mechanical and metabolic performance of humans facilitates prediction and optimization of power output on the one hand, and targeted design and innovative control of powertrain components on the other hand.The possible human power output during cycling depends on several factors such as age, weight, height, gender and fitness. An individual's maximum heart rate, maximum oxygen demand, and maximum mechanical power are some of the parameters used to optimize fitness levels. Mechanical power is also calculated here from cadence and torque.
Pedaling frequency is the term used to describe the speed of pedaling when cycling and can also be referred to as cadence. This cadence is usually measured in revolutions per minute. Different people cycle at different cadence rates, depending on personal preference. In addition, the cadence of the same person varies depending on the power required. Variation in cadence affects heart rate, oxygen demand, blood lactate levels, metabolic efficiency, and energy expenditure. Torque is the product of the net force applied to the pedal and the crank length and is measured in Newton meters. Torque at the crank consequently varies depending on the crank angle and, in the case of the bicycle, is used to overcome all driving resistance.
Towards the prototype research vehicle, the integration of comprehensive sensor technology and the use of rapid control prototyping tools created a research platform as a "proof of concept" for a "muscuhybrid" powertrain, which serves both to gain knowledge and to evaluate the driving experience. This research platform enables further research on different control strategies that create a different driving experience. Likewise, innovative approaches in the field of energy management can be implemented and the delivery of mechanical power by humans can be better understood.
The lateral guidance of the vehicle is not controlled as in traditional passenger cars with a steering wheel in front of the driver, as the leg movement would collide with this. Instead, the driver sits in a large steering wheel that is open at the top, i.e. an arc segment that encloses the driver from below. The so-called "steering bow" offers advantages in terms of access, especially for sporty seating positions, does not obstruct the view and creates space for the legs while using the pedal drive (human-hybrid). By not restricting the view, the displays of the e-jet can be designed much more freely and adapted to the needs of the driver. Last but not least, the "Steering-bow" supports an intuitive and highly dynamic driving experience.
The ongoing efforts to reduce air resistance and improve vehicle dynamics of motor vehicles require the development of novel aerodynamic concepts. In addition to passive measures on vehicles, active aerodynamic systems (AAS) are increasingly used to influence vehicle aerodynamics. In the E-Jet research vehicle, multi-part active wing systems derived from aviation are used on both the front and rear axle. This allows additional downforce to be generated during different driving maneuvers and air resistance to be influenced in a targeted manner. Simulation shows that when using AAS, a significant increase in maximum cornering speed is achieved by increasing the downforce compared to the reference condition. Furthermore, a significant reduction of the braking distance is possible. Active aerodynamic systems thus offer great potential for opening up a new dimension in both driving dynamics and energy efficiency.
Hans Hermann Voss-Stiftung, IKV, ISF