# Dynamic Energy Efficient Control of Induction Machines Using Anticipative Flux Templates
## 1 Introduction  
Electric drives have always been a key component of any automated process. The ongoing drive to automate every single aspect of a production process combined with the added intelligence of the Fourth Industrial Revolution have induced a renewed research interest in electric drives. In parallel, we are witnessing the widespread adoption of electric vehicles, in particular cars, trucks, automated logistics vehicles, and electric bikes. Whenever mentioning electric mobility, it is necessary to evaluate the technological and sociological boundaries. The restricted capacities of energy storage technologies are a limiting factor. The concerns about negative environmental impacts throughout the production process, lifetime, and dismantling process of a product must be addressed. For these reasons, an electrically propelled future must use energy, cost, and resource efficient drive systems. Highly energy efficient electric machines are typically obtained by using permanent magnet or separately excited synchronous machines. However, permanent magnets cause a variety of issues [1]. From an environmental point of view, the extraction of the needed rare earth materials is a polluting process, and these materials can yet not be recycled after the motors' lifetime. The global market for rare earth materials is nearly a single source situation, which is not desirable for any manufacturer, as they are furthermore confronted with high prices and high price fluctuations. The manufacturing process of both permanent magnet and separately excited synchronous machines is complex, which also results in higher overall costs for this machine type. Induction machines are used in industrial applications and electric mobility due to their very simple design and operation compared to other machine types. This simplicity leads to a more cost and resource efficient manufacturing process. No permanent magnetsare required, which eliminates most of the negative aspects mentioned above. This is the case for synchronous reluctance machines as well. An energy efficiency comparison was given in [2], and an easy optimization method based on minimal power per torque was given in [3]. In addition, there are particular measures required in the field weakening operation of induction machines compared to permanent magnet synchronous machines. Induction machines are well known for their robustness and ease of installation. However, the energy efficiency is lower compared to permanent magnet synchronous machines, in particular in the part load regime at rated flux. This is the case in many standard applications like fans, pumps, and conveyors. The energy efficiency of induction machines can be increased by appropriately adjusting the flux linkage according to a given operating point. This approach aims at minimizing the energy losses. Many techniques for implementing steady state optimization, which is at a given constant speed and a given constant torque, for induction machines are already available. Such methods can be reviewed, e.g., in [4]. One of these approaches is to search for the optimal operating point [5] or by explicitly solving the optimization problem of minimizing the losses using a machine model [6], when using scalar control. In field oriented control, the optimal flux linkage or equivalently the optimal magnetizing current can be determined using parameter based methods [7; 8], search methods [9], or a combination of parameter and search based approaches, as in [10]. Loss minimization for direct torque control was considered in [11]. These methods can be used to increase the energy efficiency in static applications such as heating, ventilation, and air conditioning, pumps, or conveyors. By increasing the energy efficiency of induction machines, they become more attractive for industrial and electric mobility applications. However, in electric vehicle applications and many industrial applications, motors will be operated in a dynamic regime with continuously changing torque and speed up to the current and voltage limits.