# Review of Advanced Medical Telerobots
## 3 Autonomy Levels
### Bilateral Teleoperation  
As mentioned in Section 2, in teleoperation architectures, the follower robot mimics the actions of a leader robot controlled by an operator. In surgical applications, typically, two arms are independently controlled by both operators. Thus the system is indeed two independent SM-SS architectures (see Section 2.1). A complementary human-robot interface (HRI), often featuring pedals, enables the operator to move the third arm handling the endoscope. Still recently, many generations of surgical robots have only relied on position-position exchanges: the follower tracks the position of the leader and reciprocally. For instance the da Vinci robot does not enable force feedback (a solution to circumvent this limitation on this specific robot has been recently proposed in [114]). Yet, as detailed in Section 2.1.1, some reports have been regularly published about the usefulness of haptic feedback in specific medical applications. Though teleoperation systems have featured force feedback for a long time in other applications (spacial, submarine, mobiles robots,...) [4; 54; 206; 312]. Figure 7: Autonomy levels, from teleoperation (**left**) to supervisory control (**right**) in teletherapy applications. This lateness in the medical field can be explained, on the one hand, by the patents of intuitive surgical that blocked the development of this market, and on the other hand, by the difficulty to measure the interaction forces during surgical tool-patient interactions, while remaining compliant with medical sanitation laws, and to efficiently transmit it to the surgeon. Hopefully, force feedback has been progressively integrated into the next generations of medical robots.The very first haptics-enabled commercialized surgical robot is considered to be the NeuroArm (IMRIS, Inc., Minnetonka, MN, USA): a telerobot designed for MR-guided biopsy and stereotaxy embedding two 3-DOF optical force sensors. It is controlled remotely by a surgeon from a robot workstation featuring several display monitors and two haptic devices. It was first introduced as a project in [315], used for a first neurosurgical procedure in 2008. In 2009, the MiroSurge telerobot from the German Aerospace Center (DLR) had similar functions to ZEUS and LARS, but with force feedback [49; 50]. Since, other robots with force feedback were introduced, such as the AQrate(r) System (KB Medical) for minimally invasive spinal surgery, Avatera (Avateramedical GmbH, Jena, Germany), MiroSurge, Revo-I(r), Senhance (2017, TransEnterix, Morrisville, NC, USA), the CMR Surgical (Cambridge, UK) Versius, the REVO-I RAS system (Revo Surgical Solutions, Seoul, Korea), or the Stryker's Mako platform for total knee and hip replacement [52]. Recent works published promising solutions for medical applications, providing haptic feedback with forces about 4 N with a resolution of 0.03 N and stiffness about 3.6 N/mm with a resolution of 0.025 N/mm [316]. One of the great features of bilateral teleoperation is the opportunity to provide scaled manipulation [317], to manipulate objects at a smaller scale and to magnify rendered forces. In medical applications, the motion of the follower effector is often scaled down to perform delicate and precise tasks. Yet, [PERSON] et al. showed that motion scaling reduces the number of errors at higher magnifications, but could also increase the task completion time [318]. Indeed, the drawback is that the attainable space is proportionally reduced, which prevents the surgeon to perform larger movements to navigate between targets. This is why a clutching approach has been rapidly integrated into medical robots: when clutched, the follower does not move and the surgeon can move the leader back to extend his movement once unclutched. However, this is repetitive and time-consuming. Recently, [PERSON] et al. introduced a self-adaptive motion scaling mechanism that adapts to the user skills and the task requirements [319].