Surgical robotic haptic force feedback system based on bioimpedance

Abstract

The application discloses a kind of surgical robot tactile force feedback systems based on biological impedance, including signal processing module, main end controller, with tension sensor and double electrode end effector and bioelectric impedance double electrode equivalent circuit.Two electrodes are respectively used subcutaneous electrode and insulated dry electrode, and are integrated into instrument end in the form of patch, and outer layer is wrapped with a layer of thin flexible glass;The input end of subcutaneous electrode and the output end of insulated dry electrode are connected to signal processing module.Tension sensor selects through-shaft tension sensor, and is connected with main end controller and instrument end by four steel wires respectively, and steel wire is shielded electromagnetic interference by graphene wrapping.The application enables the doctor who controls main end controller to obtain position information and force information of instrument end during operation, and improves force tactile feedback effect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of surgical robots in medical devices, and relates to a surgical robot tactile force feedback system based on bioimpedance. BACKGROUND

[0002] Surgical robots are medical device products integrating multiple disciplines such as medicine, machine science, biomechanics and computer science. With the development of minimally invasive surgery and related underlying technologies, they can provide support for surgeons in terms of vision, hearing and touch during surgical operations, and are used in minimally invasive surgery to achieve precise control of surgical instruments. Compared with open surgery and traditional minimally invasive surgery, robot-assisted surgery has the following advantages: ①reducing surgical wounds, faster postoperative recovery and fewer postoperative complications; ②flexible mechanical arms compatible with highly complex surgeries; ③precision of surgery and stability of surgical results; ④reducing surgeon fatigue and shortening the learning curve; and ⑤reducing radiation exposure.

[0003] The application of surgical robots at home and abroad has shown their technical superiority, but there are also some limitations, including the lack of tactile force feedback system. The operator can only compensate for tactile information through visual feedback, which increases the uncertainty and risk of surgery, thereby limiting the further development and application of surgical robots. Most of the surgical robots currently used in clinical practice use visual feedback systems. Surgeons cannot perform palpation on patients when controlling the mechanical arm to perform surgery. Therefore, the lack of tactile force feedback has become a major challenge to the development of surgical robots.

[0004] The tactile force feedback system of the surgical robot is to send the motion, position and attitude data of the operating end to the core processor in real time and accurately, and to feed back the data to the surgeon through the display system and control system, so that he can get a real surgical operation experience and ensure the safe and reliable operation of the mechanical hand. Tactile force feedback not only provides the mechanical arm with appropriate operating force, but also enables the surgeon to feel the different characteristics of soft tissue such as texture and shape, so as to distinguish pathological tissues. Surgical robots with tactile force feedback systems can enhance the surgeon's sense of presence during surgery, improve the safety and precision of surgery.

[0005] The human tactile perception is a complex bioelectric signal reaction process, to simulate the human tactile reaction, the tactile sensor of the mechanical arm must be able to digitally simulate the texture, smoothness and morphology of soft tissue. At present, Leven et al. use laparoscopic ultrasound in the robotic-assisted laparoscopic treatment of liver cancer, successfully obtain the tactile information of the tissue, and can reproduce the information in the form of two-dimensional or three-dimensional images, but whether this technology can be widely used in other surgeries needs further study, and the image reproduction of tactile information is still a form of visual compensation, which does not conform to the physiological habit of human tactile perception. SUMMARY

[0006] In order to make the mechanical arm of the surgical robot obtain the tactile force feedback, strengthen the surgical on-site feeling of the surgeon, and improve the safety and precision of the surgical robot operation, the application provides a surgical robot tactile force feedback system based on bioimpedance.

[0007] The surgical robot tactile force feedback system based on bioimpedance provided by the application can judge the position of the surgical instrument between tissues by applying signals with different frequencies to the bioelectric detection electrode integrated at the instrument tip, calculating the impedance after the signal processing module obtains the electric signal feedback, and feeding back the position information to the surgeon. At the same time, the force information of the instrument tip is obtained by the tension sensor near the instrument tip of the mechanical shaft and fed back to the surgeon, so that the surgeon can synchronously obtain the position information and the force information between tissues of the surgical instrument, which helps the surgeon to more accurately and safely complete the operation.

[0008] The application adopts the following scheme to solve the tactile force feedback problem: a surgical robot tactile force feedback system based on bioimpedance, which comprises a signal processing module, a sensor 3, a master controller, a mechanical shaft, and an instrument tip of a mechanical arm. The instrument tip comprises a double-electrode structure, a first electrode 1 adopts a subcutaneous electrode, can form an electrode with an electrolyte solution interface with as small a potential difference as possible, and a second electrode 2 adopts an insulated dry electrode. The input end of the first electrode 1 is connected to the signal processing module, and the output end of the second electrode 2 is connected to the signal processing module. The signal processing module is connected to the master controller. The master controller, the sensor 3 and the instrument tip are connected by four steel wires, and the instrument tip is also connected to soft tissue. The master controller controls the movement of the instrument tip through the steel wire, the sensor 3 measures the tension generated by the movement tremor of the steel wire, and feeds back the tension to the master controller, so that the operating surgeon obtains the force information of the surgical instrument in the soft tissue. The master controller effectively combines the obtained position information and force information to obtain the tactile force feedback.

[0009] Further, the first electrode 1 and the second electrode 2 are integrated in a patch type at the end of the instrument, and are arranged in three layers, the third layer is a patch base layer, the third layer is arranged in the inside of the end of the instrument or at the bottom of the electrode 1 and the electrode 2; the second layer is an electrode layer; and the uppermost layer is an insulation shielding layer.

[0010] Further, the sensor 3 is a through-shaft tension sensor, which is used for detecting the tension generated by the movement of the steel wire.

[0011] Further, the insulation shielding layer is made of flexible glass, which has high hardness and high air tightness, so that the electrode is prevented from being damp and electric leakage.

[0012] Further, the outermost layer of the steel wire is wrapped by graphene, so that electromagnetic interference is prevented.

[0013] Compared with the prior art and method, the present application has the following advantages:

[0014] 1. The present application relates to a surgical robot tactile force feedback system based on bioimpedance, which maps the force application of the end effector of the mechanical arm between tissues to the master controller, restores the on-site feeling of the doctor during operation, so that the operation risk is reduced and the operation precision is improved.

[0015] 2. The present application relates to a surgical robot tactile force feedback system based on bioimpedance, which improves the integration degree by integrating the force sensor at the mechanical shaft close to the end of the instrument and adding a double electrode to the end effector of the mechanical arm to form a current loop.

[0016] 3. The present application relates to a surgical robot tactile force feedback system based on bioimpedance, which directly acquires the force information of the end effector by receiving the tremor of the end of the instrument through the tension sensor, so that the modification cost is saved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A schematic diagram of a surgical robot tactile force feedback system based on bioimpedance.

[0018] Figure 2 A bioelectric impedance double electrode equivalent circuit model.

[0019] Figure 3 A schematic diagram of an electrode integration mode.

[0020] Among them, the first electrode 1 is a stimulating electrode; the second electrode 2 is a detecting electrode; and the sensor 3 is a through-shaft tension sensor. Figure 2 In the left drawing, Re is the resistance of extracellular fluid; Ce is the parallel capacitance of extracellular fluid; Rm is the resistance of cell membrane; Cm is the parallel capacitance of cell membrane; Ri is the resistance of intracellular fluid; and Ci is the parallel capacitance of intracellular fluid. Figure 2In the right figure, Ri is the equivalent internal fluid resistance of the biological tissue, Re is the equivalent external fluid resistance of the biological tissue, Cm is the equivalent membrane capacitance of the biological tissue. Layer 1 is an insulating shielding layer; layer 2 is an electrode layer; layer 3 is a patch substrate layer. DETAILED DESCRIPTION

[0021] The application is based on the requirements of the clinical biomechanics of the surgical robot mechanical arm, such as elastic modulus, stress, strength, biocompatibility, etc., and combines the characteristics of bioelectrical impedance measurement to transform the end effector of the mechanical arm and design and manufacture a mechanical arm with a tension sensor and a double electrode structure.

[0022] First, two bioelectric detection electrodes are integrated at the end of the instrument, which are respectively a first electrode 1 and a second electrode 2. A signal processing module of a surgical robot system applies a signal of a certain frequency to the first electrode 1. When the end of the instrument contacts the soft tissue, a complete bioelectrical impedance current loop is formed. At this time, the second electrode 2 receives the electrical signal transmitted by the soft tissue because it is connected to the bioelectrical impedance current loop. The electrical signal is fed back to the signal processing module through the output end of the second electrode 2. The signal processing module calculates the bioelectrical impedance according to the bioelectrical impedance double electrode equivalent circuit model, so as to obtain the depth of the surgical instrument in the soft tissue. The signal processing module feeds back the position information (the depth of the surgical instrument in the soft tissue) to the master controller of the surgical robot system. Secondly, a sensor 3 is installed near the end of the instrument, which is connected to the master controller of the surgical robot system and the end of the instrument by four steel wires. The steel wires are used to control the movement of the end of the instrument and to transmit force information. The sensor 3 measures the tension of the steel wire through the tremor generated by the movement of the instrument, and feeds back the force information to the master controller through the four steel wires between the master controller and the sensor 3. The master controller of the surgical robot system obtains the position information of the surgical instrument in the soft tissue from the signal processing module and obtains the force information of the surgical instrument when cutting, suturing and other operations on the soft tissue from the tension sensor. The synchronous acquisition of the position information and the force information achieves the purpose of receiving the tactile force feedback, so as to facilitate the surgeon to control the operation force and improve the safety of the operation.

[0023] The first electrode 1 is selected to be a subcutaneous electrode, which can form an electrode with an electrolyte solution interface with as small a potential difference as possible.

[0024] The second electrode 2 is selected to be an insulating dry electrode, which has the advantages of stability and anti-interference.

[0025] The input end of the first electrode 1 and the output end of the second electrode 2 are connected to the signal processing module.

[0026] The sensor 3 is selected to be a through-shaft tension sensor, which is used to detect the force of the pulled steel wire.

[0027] The outermost layer of the steel wire is wrapped with graphene to prevent electromagnetic interference.

[0028] For the tactile force detection of the end effector of the surgical robot manipulator, according to the structure of the end effector, the detection element is generally installed at four positions of the joint driving module of the surgical robot, the extraperitoneal mechanical shaft, the intra-peritoneal mechanical shaft and the instrument end. In the present application, the end tactile force detection method of the rear sensor is adopted, the first electrode 1 and the second electrode 2 are integrated at the instrument end, the sensor 3 is installed at the mechanical shaft close to the instrument end, and the main end controller, the sensor 3 and the instrument end are connected through four steel wires.

[0029] As shown in the accompanying Figure 1 As shown in the accompanying Figure 2 When the instrument end contacts the soft tissue to form a complete bioelectric impedance current loop with the soft tissue, the signal processing module applies a low-frequency signal (lower than 1 MHz) to the electrode 1, and the second electrode 2 detects the electrical signal and outputs it to the signal processing module. The signal processing module calculates the bioelectric impedance according to the bioelectric impedance double electrode equivalent circuit model, and the depth of the instrument end in the soft tissue can be obtained. The signal processing module feeds back the position information to the main end controller, so that the operator can obtain the position information of the surgical instrument in the soft tissue. At the same time, the main end controller controls the movement of the instrument end through the steel wire, and the sensor 3 measures the tension generated by the movement tremor of the steel wire and feeds back the tension to the main end controller, so that the operator can obtain the force information of the surgical instrument in the soft tissue. The main end controller effectively combines the obtained position information and force information to obtain the tactile force feedback.

[0030] The signal processing module and the main end controller are self-modules of the surgical robot system; in order to ensure that the potential difference between the electrode and the electrolyte solution is as small as possible, the first electrode 1 is a subcutaneous electrode; in order to ensure that the bioelectric impedance double electrode circuit is stable and can resist interference, the second electrode 2 is an insulated dry electrode; the sensor 3 is a through-shaft tension sensor, which has similar working environment conditions (temperature 0~40℃, relative humidity 95%) to the human body, and is used to detect the tension generated by the main end controller pulling the steel wire; in order to effectively shield electromagnetic interference, the outermost layer of the steel wire is wrapped with graphene.

[0031] As shown in the accompanying Figure 2As shown, in the bioelectrical impedance dual-electrode equivalent circuit model, Re represents the resistance of the extracellular fluid, Ce represents the parallel capacitance of the extracellular fluid, Rm represents the resistance of the cell membrane, Cm represents the parallel capacitance of the cell membrane, Ri represents the resistance of the intracellular fluid, and Ci represents the parallel capacitance of the intracellular fluid. In the low-frequency range (below 1MHz), the leakage resistance Rm of the cell membrane is very large and can be considered an open circuit. The parallel capacitances Ci and Ce of the intracellular and extracellular fluids are very small and can also be considered open circuits. Since biological tissues are composed of a large number of cells and are collections of many cells, the circuit model of biological tissues can also be represented by an appendix. Figure 2 The circuit shown in the right figure is used as an equivalent, where Ri represents the equivalent internal fluid resistance of the biological tissue, Re represents the equivalent external fluid resistance of the biological tissue, and Cm represents the equivalent membrane capacitance of the biological tissue.

[0032] As attached Figure 3 As shown, the present invention integrates the first electrode 1 and the second electrode 2 at the end of the device in a patch-type manner, which consists of three layers. Layer 3 is the patch base layer, which is located inside the end of the device or at the bottom of the first electrode 1 and the second electrode 2. Layer 2 is the electrode layer, which is composed of electrode 1 or electrode 2. Layer 1 is an insulating shielding layer, which is made of flexible glass. Its high hardness and high airtightness prevent the electrodes from getting damp and leaking electricity.

[0033] The scope of this invention is defined by the claims and their equivalents.

Claims

1. A bioimpedance-based haptic force feedback system for a surgical robot, characterized by, It comprises a signal processing module, a sensor (3), a master controller, a mechanical shaft and a mechanical arm instrument tip. The instrument tip comprises a double electrode structure, a first electrode (1) is a subcutaneous electrode, which can form an electrode and an electrolyte solution interface with the smallest possible potential difference; a second electrode (2) is an insulated dry electrode; the input end of the first electrode (1) is connected to the signal processing module; the output end of the second electrode (2) is connected to the signal processing module; the signal processing module is connected to the master controller, and the signal processing module feeds back position information to the master controller; the master controller, the sensor (3) and the instrument tip are connected by four steel wires, and the instrument tip is also connected to soft tissue; the master controller controls the movement of the instrument tip through the steel wire, the sensor (3) measures the tension generated by the movement tremor of the steel wire and feeds back the tension to the master controller, so that the operating doctor obtains the force information of the surgical instrument in the soft tissue, and the master controller effectively combines the obtained position information and force information to obtain the tactile force feedback.

2. The bioimpedance-based haptic force feedback system for a surgical robot of claim 1, wherein, The integration mode of the first electrode (1) and the second electrode (2) in the instrument tip adopts a patch type, which is arranged in three layers, layer 3 is a patch base layer, layer 3 is arranged inside the instrument tip or at the bottom of the first electrode (1) and the second electrode (2); layer 2 is an electrode layer; the uppermost layer 1 is an insulating shielding layer.

3. The bioimpedance-based haptic force feedback system for a surgical robot of claim 1, wherein, The sensor (3) is a through-shaft tension sensor, which is used to detect the tension generated by the movement of the steel wire.

4. The bioimpedance-based haptic force feedback system for a surgical robot of claim 2, wherein, The insulating shielding layer is made of flexible glass, which has high hardness and high airtightness, so as to prevent the electrode from being damp and electric leakage.

5. The bioimpedance-based haptic force feedback system for a surgical robot of claim 1, wherein, The outermost layer of the steel wire is wrapped with graphene, which prevents electromagnetic interference.

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