# Review of Advanced Medical Telerobots
## 2 Medical Telerobotic Topologies
### Multilateral Teleoperation  
A natural extension of the conventional use of bilateral telerobotic systems is multilateral telerobotic systems (see [4] and references therein). Multilateral teleoperation is an upgraded version of conventional bilateral SL/SF teleoperation systems, which consists of more than a single set of leader-follower robotic modules. Multilateral telerobotic systems have at least three terminals which can be connected to single-port modules interacting with a remote task or a remote user. Technically, these systems can be composed of multiple leader robotic modules and multiple follower robotic modules. According to the topological structure of multilateral systems, they are categorized as Single-leader/Multi-follower (SL/MF), see for example [4; 225; 226; 227; 228; 229], Multi-leader/Single-follower (ML/SF), see for example [230; 231; 232], and Multi-leader/Multi-follower (ML/MF), see for example [4; 233; 234; 235; 236; 237; 238; 239; 240; 241; 242; 243; 244; 245; 246]. These systems allow for the realization of a variety of new tasks that require multiport communication between distributed modules such as collaboration and interactions between multiple network terminals, multiple robots, and multiple operators enhancing efficacy, precision/accuracy, dexterity/manipulability, loading capacity (through distributed power) and handling capability through joint task conduction and shared autonomy, see for example [247; 248; 249; 250; 251; 252; 253; 254; 255; 256; 257; 258; 259; 260; 261; 262; 263; 264; 265; 266; 267; 268; 269; 270; 271; 272; 273; 274; 275; 276; 277; 278; 279; 280; 281; 282; 283; 284; 285; 286; 287; 288; 289; 290; 282; 284; 285; 286; 287; 288; 289; 291; 288; 289; 292; 300; 301; 302; 303; 304; 305; 306; 307; 308; 309; 310; 311; 312; 313; 314; 315; 316; 317; 318; 319; 320; 321; 322; 323; 324; 325; 326; 327; 328; 329; 330; 331; 332; 333; 334; 335; 336; 337; 338; 339; 340; 341; 342; 343; 344; 345; 346; 347; 348; 349; 350; 351; 352; 353; 354; 355; 356; 357; 358; 359; 360; 361; 362; 363; 364; 365; 366; 367; 368; 368; 369; 370; 371; 372; 373; 374; 375; 376; 377; 378; 379; 380; 381; 382; 383; 384; 385; 386; 387; 388; 388; 389; 390; 391; 392; 393; 394; 395; 396; 397; 398; 399; 400; 401; 402; 403; 404; 405; 406; 407; 408; 409; 410; 411; 412; 413; 414; 415; 416; 417; 418; 419; 420; 421; 422; 423; 424; 425; 426; 427; 428; 429; 430; 431; 432; 433; 434; 435; 436; 437; 438; 439; 444; 450; 451; 452; 453; 454; 455; 456; 457; 458; 459; 4 at the follower position controller so that the two surgeons can take turns to conduct the surgery when the other surgeon would go to an observation mode. This has been realized using the dual-user da Vinci surgical system when an expert surgeon conducts a task and then observe the conduction of the same task by the novice trainee [218; 269; 270; 271; 272; 273; 274]. Instead of switching, fusion scenarios have been conducted when the motions of the two surgeons are fused through a mixing matrix to control the follower robot. This would allow reducing the errors and increasing accuracy [247; 253; 258; 266; 269; 270]. The mixing matrix is usually calculated and set based on the expertise level of the surgeon before the operation. In a more advanced manner, it is suggested that the performance of the two surgeons can be concurrently calculated, and the authority level of the surgeons can be shared based on the corresponding performance matrix, which can change and evolve [258; 275; 276]. The performance measure can be calculated on the fly based on metrics like the smoothness of motion, task completion time, the economy of motion, gaze stability [150; 207; 247]. In the literature, techniques such as fuzzy logic algorithms have also been utilized to evaluate the performance of the two surgeons in real-time and adaptively calculate the authority level to be assigned [240; 241; 258; 277].