## 4 Results
### Discussions  
The results from Sections 4.1 and 4.2 show the successful application of the DCP extension for coupled test bench operation with an ICE and an EM to represent a hybrid electric powertrain. The successfully implemented communication results, above all, in the negligible deviations between reference and actual values for the remote-controlled slave, the EM, as well as the resulting additional EM test bench operations, such as the execution of dynamic gear shift operations. Figure 9: Reference \(M_{EM,REF}\) and actual torque \(M_{EM,ACT}\) of the EM in a WLTC compared to the maximum permitted torque \(M_{EM,MAX}\). In addition to the functional test benches and a suitably designed communication, a successful coupling also requires a robust superimposed control unit for distributing the required torques to the combustion engine and the electric motor. This function therefore acts like a superimposed control loop with the aim of realizing the torque desired by the driver in the shortest possible time. To this end, the requested torques are compared with the torques reported back by the combustion engine and electric motor, and readjusted accordingly depending on the situation. In the case of functions with control loops and feedback, attention must be paid to the dead times of the system to be controlled. If the dead times of the whole system exceed a certain value, a stable operation of the superimposed control unit is no longer possible. In this research approach, the high latency in the torque measurement by an external power measuring device is identified as the main cause for the high dead time. As a remedy, the actual torque provided to the hybrid controller was calculated and the measured torque was only used for measurement data recording and validation. This allowed the dead time for measurement to be bypassed and the control loop to remain stable. An integrated measuring device or other measuring systems may enable the use of the measured torque. In the case of torque distribution by the hybrid controller, the dead time can also result from the following parts:  
* Data transmission of the torque reference points from the hybrid controller to the ECU;
* Adjustment of the currents for the corresponding reference torque;
* Recording of the measured torque in the engine control unit;
* Data transmission of the measured torque to the hybrid controller. The definition of a safe state for each test bench and the monitoring of the communication for connection failures is advisable. Since control of the test benches is handed over to an external master for the duration of the tests, errors may not be detected by the master in time, and unreasonable reference values may be requested in the event of a connection failure. A detailed monitoring strategy is highly recommended, as the probability of a test bench malfunction by an external entity is higher than by an on-site operator. If the test bench detects an error, control must be withdrawn from the master and a safe operating state must be defined. In addition, the master must be informed about the termination of the simulation, so that the test is prematurely terminated. The safe state cannot be defined in general, and depends on the test bench and the periphery. Figure 10: Accelerator pedal \(\alpha_{HC}\) and throttle valve position \(\alpha_{ICE}\) in a WLTC compared to the actual torque of the EM \(M_{EM,ACT}\). A conditioning of the components for the coupling of hardware is necessary, especially under thermal preconditions. This procedure also offers the advantage that the test bench reference value limits are derived in a standardized way and can be integrated directly into the software for the test run. In addition, for safety reasons, the limits should also be communicated to the other participants as part of the DCP protocol in order to prevent incorrect reference value requests, and thus, possible undesirable system behavior.