TORQUE CONTROLLED ELECTRIC DRIVE - FUNCTIONAL SAFETY
The electrification of mobility is unstoppable. Electric drives in the automobile and in the bicycle determine the everyday life in all news channels. The advancement of electric motors in terms of efficiency and power density has experienced a new renaissance through electric mobility. Completely developed electric motors are experiencing a new dimension of possible applications. As a result of these emerging markets, the demands on the electric motors are increasing not only in terms of their efficiency, long-term stability and material properties, but also in terms of online operating information on the current state of the electric motors. Important parameter for this is the efficiency that means the ratio of the input power in terms of output power, but also rotational speed, radial run-out and concentricity of the drive shafts. In order to determine these input and output characteristics, a large number of sensors are integrated into the electric motors. In addition to rotation speed sensors, rotation angle sensors, current and power sensors are important input variables for controlling the electric motors. These input variables make it possible to implement an „open loop“ control of the electric motors. This „open loop“ control is based on the assumption of certain control characteristics of the electric motor which are developed on the basis of theoretical models. The tuning of these control maps can be finely tuned to any electric motor in an EOL (End of Line) test and a final calibration. Thus, control accuracies for the output torque of up to 5% FS are possible
Due to temperature, aging effects in operation and normal material aging, however, the behavior of the electric motors and thus the model which serves as a basis for the map control as an assumption, which results in that the control of the electric motor deviates from the optimum operating point and thus loses efficiency, ie. consumes more energy than is actually necessary. The energetic balance of electric motors is the one aspect of the working point consideration. For safety critical applications, which means whenever an interaction between man and machine takes place, the faulty regulation can become a danger. This can be critical in applications in the field of robotics, in which electric motors move a mechanic that works on to man, or in electric mobility, where electric motors drive the car or e-bike in which people are. Magnetic Sense is working to provide a solution for integrating torque measurements directly into applications using contactless magnetic inductive torque sensor technology. Sample sensors realized with this technology are in initial field trials with customers. This new technology of the magnetic inductive torque sensor in Magnetic Sense‘s electric motor makes it possible for the first time in a series application to measure torques under commercially interesting conditions. The integration of a torque sensor in the output of torque sensors, it would thus be possible to realize a „closed loop“ control of the electric motor. That Due to the closed control loop, the input manipulated variable for the electric motor can be specified by means of voltage / current and checked directly with the torque at the output. With this option, the operating point of the electric motor can be implemented independently of a model-based control and the associated aging problems. The magnetic inductive torque sensors from Magnetic Sense can be optimized for customer-specific installation space and can therefore be integrated into almost any application.
Magnetic Sense torque sensor specification
- Contactless measuring principle
- Insensitive to mechanical overload
- Digital literarized output signal
- Robust against interference fields
- No mechanical or magnetic machining of the measuring point necessary
- No specific requirements for the material of the shaft
- No aging effects
