# Review of Advanced Medical Telerobots
## 2 Medical Telerobotic Topologies
### Single-Leader Single-Follower Topology (SL/SF)
#### 2.1.1 Sensory Augmentation through SL/SF Telerobotic Surgery
It should be noted that, due to the neurophysiology of haptics sensation, distracted force feedback may sometimes be even worse than not having the feedback at all. This is because humans rely heavily on haptics modality for conducting delicate tasks; thus, high quality of force reflection can significantly improve the performance of fine motor control of the surgeons using the robotic surgical system [146; 170; 171] while a low quality of force feedback may potentially defeat the purpose. Degraded force feedback can degrade the performance by misleading motor control of surgeons, when comparedwith the lack of force feedback, which would push surgeons to put all the weights of sensory awareness on to the visual channel [145; 170; 171; 172; 173; 146; 174; 175; 176; 177] which in many cases has been considered as a successful practice through visuohaptic skill development. It should also be noted that the instability challenge will be magnified significantly if the leader and follower robotic systems are placed in two distant locations requiring a significant networked connection, which would result in variable time delays with significant jitter, data loss, and latency [172; 174; 175; 176; 177]. With the invention of 5G and beyond networked systems and major promise in maximizing the reliability of data transfer while minimizing the time delay, it is now possible to think about solutions that can not only address the stability [178; 179] of local leader-follower telerobotic surgical systems but also networked telerobotic surgical systems. For this purpose, advanced control techniques have been recently proposed based on small gain control theory [64; 180] and strong passivity control theory [7; 85; 166; 181], which can potentially rely on an ultra-reliable 5G communication network to guarantee the stability and to maximize the performance of force reflection. There are several different studies on the amount of allowable delay in a telerobotic system, especially when used for surgical operation. Various numbers are given in the literature, mainly in the range of 100 to 200 ms. However, it should be noted that the amount of delay depends on many different aspects. For example, the type of operation and the sensitivity of the surgical submissions can significantly affect the allowable delay. For example, if the surgeon is operating near to a beating heart, the acceptable delay would be very low compared to some other surgeries when the organ is less sensitive or when it does not have motion. This is about the feedforward path for position control at the follower side. It should be noted that in the case of force-feedback teleoperation, the delay can (a) affect the perception of the stiffness of the environment, and (b) can destabilize the system resulting in safety concerns which should be stabilized by adding controllers which can then further affect the fidelity of force feedback. Because of all the reasons mentioned above, it is not possible to provide a fixed number for the acceptable delay in a medical telerobotic system. Readers will find more recent information on this topic in [183; 27; 182]. Thus with the use of advanced technology, including ultra-fast communication, advanced instrumentation, and algorithmic stabilizers [7; 64; 82; 85; 150; 166; 180; 181; 184], it can be envisioned that the next generation of telerobotic surgical systems is equipped with means of high-fidelity haptics reflection enabling surgeons to not only benefit from an augmented vision but also augmented haptic sensory feedback.