## 1 Introduction
This technique is also known as image-guided insertion; however, guidance is not continuous and there is no feedback control system. A robotic system integrated with a force sensor also provides useful feedback information that has the potential to reduce the trauma. Studies have found that damage to the inner ear are directly associated with the forces exerted by the EA on the inner structure during the insertion [18, 19, 20]. Some studies also suggested that ultra-low-speed insertion with a robotic tool also helps minimize the insertion forces [21, 22, 23]. Such systems cannot provide local force profiles, and they can only have start-stop feedback control. We have considered complex electrical impedance of electrode contacts as sensing elements, as all commercially available CI systems have impedance measuring capabilities. However, the measurement system can only record impedance magnitude and is used for post-operative check of electrodes' functioning (working, short, or open circuit). Impedance measuring of an electronic circuit would need some modifications to be used for continuous recording of complex impedance during insertion. Impedance sensing exploits the change in chemical reactivity around electrodes in a conductive material (i.e., perilymp in ST) that changes due to its surroundings (change in amount of fluid between electrode and wall, different tissue structure inside ST) [24]. Studies have shown that there is a relation between electrode impedance recording and their distance from the ST walls during insertion. A number of research groups have demonstrated this fact to various degrees using different stimulation approaches (monopolar, bipolar), electrode array types (straight, perimodiolar), insertion techniques (standard insertion technique (SIT), advance off style (AOS)), and ST modalities (plastic model, cadaver) [25, 26, 27, 28]. We have chosen the bipolar impedance measurement method as our sensing modality as previous studies [25,26] have shown good promise for its efficacy for EA-wall distance prediction. Having said that, another study [29] has shown that the tetrapolar impedance measurement technique reduces noise/artefactsat the electrode-electrolyte junction. Tripolar and tetrapolar impedance measurement also needs to be investigated in cochlear implantation. Electrical impedance is also used for detection of EA insertion failure and translocation [30; 31; 32]. Most recently, electrode impedance recordings were used for insertion depth estimation [33]. The limitations of the above-mentioned systems are that they were tested as only the sensing modality, and they were not tested as a feedback system that can predict, as well as make, corrective measures during insertion. Additionally, the final placement of electrode array into ST mainly depends on the insertion angle or trajectory; however, there is limited intra-operated information regarding the optimum trajectory. The aim of the current study is to utilise complex impedance recordings for the development of a complete feedback loop system. This system compromises an actuation unit, impedance measuring unit, machine learning classifier for trajectory prediction, and feedback control unit. This system provides a data-driven approach and is experimentally tested for prediction and correction of EA trajectory during insertion in a plastic ST model.