Soft tissue force control using active observers and viscoelastic interaction model

Abstract

Controlling the interaction between the robot and living soft tissues has became an important issue as the number of robots inside the operating room increases. Many research works have been done in order to control this interaction. Nowadays, researches are running in force control for helping surgeons in medical procedures such as motion compensation in beating heart surgeries and tele-operation systems with haptic feedback. The viscoelasticity property of the interaction between organ tissue and robotic instrument further complicates the force control design which is much easier in other applications by assuming the interaction model to be elastic (industry, stiff object manipulation, etc.). In order to increase the performance of a model based force control, this work presents a force control scheme using Active Observer (AOB) based on a viscoelastic interaction model. The control scheme has shown to be stable through theoretical analysis and its performance was evaluated and compared with a control scheme based on a classical elastic model through experiments, showing that a more realistic model can increases the performance of the force control.

Hunt–Crossley model based force control for minimally invasive robotic surgery

“…To better describe the complex viscoelastic properties of soft tissue contact, more sophisticated models have been proposed. The Kelvin-Boltzmann model is one of the linear viscoelastic models that best describes these properties [19]. To improve modeling accuracy, the nonlinear properties of soft tissues must be considered as well, and it is necessary to explore nonlinear models like the Hunt-Crossley model, which has been reported as a more realistic option from the physical point of view.…”

“…The Kelvin-Boltzmann model is shown to be superior to elastic and other linear viscoelastic contact models in force control for soft tissues by the recent works [19]. Therefore, for the simulation studies of this section and the experimental studies in next section, only the elastic and Kelvin-Boltzmann model based controllers are considered for performance comparison with the Hunt-Crossley model based control method.…”

“…(19), (20) and (21), the relationship between contact force F e and control input U i along one axis can be written as…”

“…Such kind of linear contact models include Maxwell model, Kevin-Voigt model, Kelvin-Boltzmann model, etc. Recent works show that robot-tissue force control based on Kelvin-Boltzmann model outperforms control methods based on traditional elastic model in terms of rise time and stability [19]. On the other hand, nonlinear models, such as the Hunt-Crossley model, are expected to be more accurate for describing the real behavior during the contact with soft human tissues [18,20].…”

Polytopic model based interaction control for soft tissue manipulation

“…Another relevant work in the topic of force tracking in beating heart surgery was published by Liu et al, utilizing the Kelvin-Boltzmann viscoelastic model [8]. Moreira et al introduced a method for soft tissue force control using active observers and a viscoelastic interaction model, confirming that using a realistic tissue model can increase the performance of the force control [9]. Force control has also been an emerging field of interest in robotic catheter cardiac ablation [10] and in minimally invasive surgery [11].…”