A force-slip detection minimally invasive surgery robot end effector

Abstract

The application discloses a minimally invasive surgery robot end effector for force-slip detection, and the clamping surface of a first clamp and a second clamp is provided with a groove for mounting a flexible deformation layer and a force-slip sensor, and the force-slip sensor is close to the inner side of the groove; the flexible deformation layer is provided with a first contact point on the side close to the force-slip sensor; the direction from one end of the first clamp and the second clamp to the other end is the longitudinal direction, the first contact point is arranged in a vertical and horizontal manner, three groups of first contact points are arranged in the longitudinal direction, and each group is composed of four first contact points; the first contact point is arranged in one-to-one correspondence with a piezoresistive cantilever beam of the force-slip sensor; when the first clamp and the second clamp clamp an object, the flexible deformation layer is deformed to make the first contact point trigger the piezoresistive cantilever beam of the force-slip sensor to be deformed, so as to realize decoupling of three-dimensional force information and slip information according to the deformation of the force-slip sensor. The design that the piezoresistive cantilever beam arranged in one-to-one correspondence with the first contact point on the force-slip sensor forms twelve detection units can improve the sensitivity and reliability of perception, and further helps to improve the action accuracy of the end clamp.

Description

Technical Field

[0001] This invention relates to an end effector for a minimally invasive surgical robot with force-slip detection, belonging to the field of medical device technology. Background Technology

[0002] Surgical robots, lacking force and slip detection capabilities, pose multiple risks in practical clinical applications. While commercial robots, such as the da Vinci Surgical System, exhibit excellent operational precision, their force-slip feedback mechanisms rely on visual judgment rather than direct mechanical and slip distance data. This prevents surgeons from perceiving the true contact force between instruments and tissues. For example, in gastrointestinal tumor resection, approximately 18% of intraoperative perforations are caused by uncontrolled clamping forces or tissue slippage. Experiments show that systems without integrated force feedback have operational force errors as high as ±3N, exceeding the safety threshold by 2.5 times. Furthermore, undetected slippage can lead to sudden instrument displacement; for instance, the cystic duct slippage rate in laparoscopic cholecystectomy is as high as 8.7%, resulting in secondary injuries such as bile leakage. In addition, the lack of slippage detection significantly reduces surgical efficiency, requiring surgeons to repeatedly adjust instrument positions. For example, rectal cancer surgery can be extended by an average of 45 minutes, and even a slippage of only 0.1mm during vascular anastomosis can cause the restenosis rate to surge from 3% to 12%. The above facts demonstrate that force feedback and slip feedback play a significant role in surgery. Integrating force sensing and slip sensing functions into surgical robot systems can reduce operational risks and improve surgical outcomes, showing promising research prospects and application potential.

[0003] Although no RMIS system integrating force feedback and slip detection has yet entered clinical practice, animal experiments have validated its dual value: introducing force feedback can reduce the peak suture force during surgical knot tying from 3.5-4.2N to 2.0±0.8N (close to artificial levels), while the slip detection system can reduce tissue displacement error from 0.5mm to 0.05mm. For example, in porcine intestinal separation experiments, force-slip collaborative control reduced the perforation rate from 12% to 2% and the rate of vascular miscutting by 60%. Experiments show that introducing force feedback and tissue slip feedback into RMIS systems can reduce errors and unintentional damage, improve surgical success rates, and shorten surgical operation time. Therefore, the introduction of force-slip feedback into minimally invasive surgery is urgent. In recent years, force-slip feedback has received considerable attention and research in robot-assisted minimally invasive surgical systems, but due to the flexibility of endoscopes and the limitations of operating space, adding force sensors is a particularly challenging task. To date, most research on force-slip sensors on endoscopic instruments is still in the early stages of development and is limited by technology and application.

[0004] Currently, while force sensing methods used in minimally invasive surgery cannot achieve precise force and slip information sensing, several methods exist. The first is direct force detection, including strain gauges (such as some models of the da Vinci EndoWrist), fiber optic sensors (such as the Medtronic Hugo system), and piezoelectric films. These methods directly acquire tissue reaction forces through contact measurement, but suffer from high costs of biocompatible materials (such as titanium alloy coatings) and signal drift issues in humid environments. Furthermore, the warm and humid environment inside the human body severely impacts sensor accuracy and lifespan. The second method is indirect force estimation, which uses motor current or joint torque to infer end-effector force (such as the Versius system). While it doesn't require additional sensors, it is susceptible to errors due to variations in robotic arm stiffness, friction, and temperature. The third method combines vision and mechanics (such as fluorescence imaging in the da Vinci surgical robot), using endoscopy and AI algorithms to indirectly calculate force magnitude through tissue deformation. However, this method has poor real-time performance and expensive imaging equipment (e.g., fluorescence modules cost over $200,000). Existing slip sensing methods include the following: The first is a multimodal tactile sensor: a flexible electronic skin that integrates pressure, vibration, and temperature signals (such as MIT's BioTac bionic fingertip), which detects changes in pressure distribution on the contact surface through a tactile array. However, miniaturization and biocompatible packaging technologies are not yet mature. The second is vibration signal analysis: using PVDF or MEMS sensors to capture high-frequency vibrations (>100Hz) to warn of slippage. However, it is not sensitive to low-frequency slippage and is easily affected by environmental noise during surgery.

[0005] As can be seen from the above, the existing minimally invasive surgical end effectors have a single force function. Therefore, designing a new type of minimally invasive surgical end effector with multi-dimensional force sensing and sliding sensing functions has become a problem that needs to be solved. Summary of the Invention

[0006] This invention provides a force-slip detection end effector for a minimally invasive surgical robot, which integrates a MEMS three-dimensional force-slip sensor with the upper and lower clamps of the end effector. Through the formation of twelve detection units, the actuator has multi-dimensional force sensing and slip sensing functions. At the same time, the design of twelve detection units can improve the sensitivity and reliability of sensing, thereby helping to improve the motion accuracy of the end effector.

[0007] The technical solution of this invention is:

[0008] According to a first aspect of the present invention, a force-slip detection end effector for a minimally invasive surgical robot is provided, comprising a first clamp 1 and a second clamp 2, wherein one end of the first clamp 1 and the second clamp 2 are rotatably engaged; the clamping surfaces of the first clamp 1 and the second clamp 2 are each provided with a groove for mounting a flexible deformable layer 3 and a force-slip sensor 4, and the force-slip sensor 4 is located near the inner side of the groove; the flexible deformable layer 3 is provided with a first contact 8 on the side near the force-slip sensor 4; with the direction from one end of the first clamp 1 and the second clamp 2 to the other end as the longitudinal direction, the first contacts 8 are arranged longitudinally and transversely, with three sets of first contacts 8 arranged longitudinally, each set containing four contacts; the first contacts 8 are arranged in a one-to-one correspondence with the piezoresistive cantilever beam 10 of the force-slip sensor 4;

[0009] When the first clamp 1 and the second clamp 2 clamp the object, the flexible deformation layer 3 deforms, causing the first contact point 8 to trigger the piezoresistive cantilever beam 10 of the force-slip sensor 4 to deform, so as to decouple the three-dimensional force information and slip information based on the deformation of the force-slip sensor 4.

[0010] Preferably, the flexible deformable layer 3 is provided with a positioning post 7 on the side near the force-slip sensor 4, and the force-slip sensor 4 is provided with a positioning hole 9. The positioning post 7 and the positioning hole 9 cooperate with each other to limit the position of the force-slip sensor 4 and the flexible deformable layer 3.

[0011] Preferably, the flexible deformable layer 3 has second contacts evenly distributed on the side away from the force-slip sensor 4.

[0012] Preferably, the second contact has a cylindrical structure.

[0013] Preferably, the force-slip sensor 4 includes a substrate, on which piezoresistive cantilever beams 10 are arranged in a one-to-one correspondence with the first contact points 8 to form twelve detection units; each detection unit uses one piezoresistive cantilever beam 10 as a strain-sensitive arm resistor and three reference arm resistors to form a Wheatstone bridge.

[0014] Preferably, the first contact 8 adopts an inverted conical or hemispherical structure.

[0015] According to a second aspect of the present invention, a force-slip detection minimally invasive surgical robot is provided, comprising a robot body and an end effector for force-slip detection of the minimally invasive surgical robot connected to the robot body as described above.

[0016] The beneficial effects of this invention are as follows: This invention employs a force-slip sensor with piezoresistive cantilever beams arranged in a one-to-one correspondence with the first contact point, forming twelve detection units. Firstly, the multi-channel design improves the tolerance to local contact unevenness, differences in tissue material, noise disturbances in individual channels, and sensitivity differences caused by manufacturing discreteness, thereby reducing the risk of missed detection. Secondly, multi-channel fusion can improve the signal-to-noise ratio of the slip characteristics, suppress false alarms caused by occasional interference, and enable the system to obtain stable and repeatable recognition results even in low clamping force, small slip, and early slip stages. Thirdly, the sensitive area is designed as a rectangular structure with its long axis along the X direction, which allows it to obtain a longer effective contact coverage and more sufficient channel response information in the clamping opening and closing direction, thereby enhancing the reliability and repeatability of slip detection in the X direction. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0018] Figure 2 This is a schematic diagram of a flexible deformable layer structure.

[0019] Figure 3 This is a schematic diagram of a piezoresistive three-dimensional force-slip sensor.

[0020] Figure 4 It is a single varistor Wheatstone bridge.

[0021] Figure 5 It is a MEMS piezoresistive three-dimensional force-slip sensor bridge circuit layout.

[0022] The labels in the figure are as follows: 1-First clamp, 2-First clamp, 3-Flexible deformation layer, 4-Force-slip sensor, 5-Fixing pin, 6-Wrist joint, 7-Positioning post, 8-First contact point, 9-Positioning hole, 10-Piezoresistive cantilever beam. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0024] Example 1: As Figures 1-5As shown, according to a first aspect of the present invention, a force-slip detection end effector for a minimally invasive surgical robot is provided, comprising a first clamp 1 and a second clamp 2, with one end of the first clamp 1 and the second clamp 2 rotatably engaged; the clamping surfaces of the upper clamp 1 and the lower clamp 2 have rectangular grooves for embedding a flexible deformable layer 3, a force-slip sensor, and a sensor 4, respectively. The force-slip sensor 4 covers the underside of the flexible deformable layer 3, i.e., the force-slip sensor 4 is located near the inner side of the groove. The flexible deformable layer 3 has a first contact point 8 on the side near the force-slip sensor 4; and the flexible deformable layer 3 has a positioning post 7 on the side near the force-slip sensor 4. The force-slip sensor 4 has a positioning hole 9, and the positioning post 7 and the positioning hole 9 cooperate to define the position of the force-slip sensor 4 and the flexible deformable layer 3; that is, when the flexible deformable layer 3 clamps tissue, the positioning post 7 and the positioning hole 9 can engage the flexible deformable layer 3 and the force-slip sensor 4 together, so that the first contact point 8 and the force-slip sensor 4 are engaged. In sensor 4, the piezoresistive cantilever beam 10 deforms upon contact, thereby decoupling three-dimensional force and slip information based on the deformation of the force-slip sensor 4. Specifically, the piezoresistive cantilever beam 10 is formed by integrating a piezoresistive resistor onto an elastic cantilever beam via ion implantation. During contact between the piezoresistive cantilever beam 10 and the first contact point 8 of the flexible deformable layer 3, the first contact point 8 transmits the deformation and vibration of the flexible deformable layer, causing the piezoresistive cantilever beam to strain accordingly. This changes the resistance of the piezoresistive resistor, thus detecting force and slip. In practical applications, the upper clamp 1 and lower clamp 2 are hinged to the wrist joint 6 via a fixing pin 5. The wrist joint 6 has a circular wire hole for passing through a thin steel wire or optical fiber. Under the action of an external drive wire rope or optical fiber, the clamps open and close to complete the clamping action.

[0025] Furthermore, the flexible deformable layer 3 in the clamping surface is designed with sealing flanges at its edges. These flanges are clamped together by the clamping structure and, in conjunction with medical-grade silicone sealing materials (such as medical silicone), enhance the overall sealing performance, ensuring the reliability and long-term stability of the device. Second contacts are evenly distributed on the side of the flexible deformable layer 3 away from the force-slip sensor 4. Although the surface of the flexible deformable layer 3 is designed with an uneven structure, the materials used are all highly elastic, low-modulus flexible biocompatible materials, such as PDMS or silicone rubber, which can undergo moderate deformation upon tissue contact, with the average contact stress far below the tissue damage threshold. Experimental verification shows that this design did not produce tissue cracks, bleeding, or indentations when in contact with fragile tissues such as pig small intestine, indicating that this contact structure provides good tissue protection while achieving force transmission amplification.

[0026] Furthermore, the first contact 8 can be processed into various structures using micromachining technology, such as an inverted cone or hemispherical structure. This structure can efficiently achieve stress concentration and transmit the small deformation of the flexible layer to the MEMS piezoresistive cantilever beam below with high sensitivity.

[0027] Furthermore, the flexible deformable layer 3 has second contacts evenly distributed on the side away from the force-slip sensor 4. For example, the second contacts adopt a cylindrical structure, so that the flat-topped contact surface of the focal point can avoid physical damage to the fragile liver (such as blood vessels and digestive tract) caused by contact deformation, thus ensuring force transmission while taking into account biocompatibility requirements.

[0028] Furthermore, the force-slip sensor 4 includes a substrate on which piezoresistive cantilever beams 10 are arranged in a one-to-one correspondence with the first contact points 8, forming twelve detection units; each detection unit uses a piezoresistive cantilever beam 10 as a strain-sensitive arm resistor and three reference resistors to form a Wheatstone bridge.

[0029] like Figure 4 As shown, each piezoresistive cantilever beam 10, together with three reference resistors R1, R2, and R3 formed by the same process, constitutes a Wheatstone bridge, where the piezoresistive cantilever beam 10 corresponds to the strain-sensitive arm resistor Rg in the bridge circuit. Thus, the 12 piezoresistive cantilever beams in the force-slip sensor 4, together with their corresponding reference resistors, form 12 independent bridge detection units, B1 to B12.

[0030] like Figure 5 As shown, with the center of the substrate of the force-slip sensor 4 as the origin, the long axis of the substrate is defined as the X-axis, the short axis as the Y-axis, and the normal as the Z-axis, where +X is to the right and +Y is upward. The 12 bridge detection units are distributed on the substrate according to predetermined spatial positions, and each detection unit independently outputs one analog voltage signal. The signal acquisition system synchronously samples the output voltages of B1 to B12 within the same sampling period and transmits them to the host computer or signal processing module, thereby forming 12 channels of timing voltage data.

[0031] During actual clamping, the external drive device controls the first clamp 1 and the second clamp 2 to close, and the flexible deformation layer 3 first contacts the tissue surface. When the tissue is clamped, the contact stress is transmitted through the flexible deformation layer 3 and the first contact point 8 to the corresponding piezoresistive cantilever beam 10, causing it to deform and resulting in a change in the bridge output voltage, thus obtaining low-frequency information characterizing the stress state. When relative slippage or a tendency to slippage occurs between the tissue and the clamps, high-frequency micro-vibrations will also be generated at the contact interface, which will also be coupled to the piezoresistive cantilever beam 10, and thus reflected as high-frequency variation components in the corresponding bridge output. Therefore, the 12-channel voltage signal simultaneously contains low-frequency information characterizing the stress state and high-frequency dynamic information characterizing the slippage state.

[0032] The 12-channel voltage data yields three-dimensional force and slip information. In this embodiment, the acquired signals are processed sequentially using the following steps:

[0033] 1. Raw signal preprocessing

[0034] First, the 12-channel raw voltage signals are subjected to zero-point correction, gain uniformity and filtering noise reduction. Then, each channel is normalized according to the baseline output under no-load conditions to eliminate the influence of bridge initial bias, power supply fluctuation, channel sensitivity difference and environmental drift on the measurement results, so as to obtain a standardized voltage signal that can be used for subsequent calculation.

[0035] 2. Band separation

[0036] Subsequently, the preprocessed 12-channel signal was band-separated into low-frequency / DC components and high-frequency components. The low-frequency / DC component is preferably a signal no higher than 100Hz, used to reflect changes in contact load between the tissue and the clamp; the high-frequency component is preferably a signal higher than 100Hz, used to reflect the micro-vibration characteristics induced by slippage. Thus, the same set of original bridge circuit outputs are fed into the force calculation branch and the slippage recognition branch respectively, achieving parallel extraction of force and slippage information.

[0037] 3. Three-dimensional force and moment calculation

[0038] For the low-frequency / DC components, based on the spatial distribution of the 12 detection units on the substrate and the response characteristics of each bridge circuit to loads in the X, Y, and Z directions, matrix transformation, differential weighting, or calibration decoupling methods are used to calculate the 12-channel low-frequency output into force components and corresponding torque information of the sensors in the X, Y, and Z directions. Furthermore, the calculation results from the two sets of sensors in the low-frequency information characterizing the force state can be obtained through vector summation, subtraction, and lever arm conversion to obtain parameters such as the operating force, clamping force (normal force), and rotational torque of the end effector.

[0039] 4. Slip Feature Extraction

[0040] The high-frequency components are input as slip-sensitive signals to the slip identification module. This module can perform rectification, envelope extraction, and root-mean-square energy calculation on the high-frequency signals of each channel, or perform time-frequency analysis such as short-time Fourier transform and wavelet transform to extract characteristic quantities that can characterize slip occurrence. These characteristic quantities may include instantaneous amplitude, energy, dominant frequency, and amplitude and phase differences between adjacent bridge paths. Since slip is usually accompanied by enhanced vibration at the contact interface and changes in spatial propagation characteristics, these characteristics can reflect whether slip has occurred, as well as the directionality and strength of the slip.

[0041] 5. Multi-channel fusion and sliding decision

[0042] Within the sliding time window, the features representing slippage extracted from the 12 channels are fused. The fusion method can be summation, weighted summation, taking the maximum value, or other statistical criteria. When the fused feature exceeds a preset threshold or meets the preset slippage determination rules, the system outputs the determination result of slippage occurrence. At the same time, it can also combine the amplitude distribution, main frequency change, and phase relationship of each channel feature to further provide the slippage occurrence time, relative direction, and slippage intensity or relative displacement / velocity information.

[0043] 6. Control Output

[0044] When the system detects slippage, it can combine the slippage determination result with the real-time normal force information and output a warning signal or closed-loop control command to the main control terminal to drive the clamp to perform adaptive force increase or decrease operations, thereby reducing the risk of tissue damage while ensuring stable tissue clamping.

[0045] Compared with the traditional 4-channel output method, the present invention adopts a 12-channel bridge synchronous output, which has the following technical effects: First, multi-channel redundancy can improve the fault tolerance of uneven local contact, differences in tissue material, noise disturbances in individual channels, and sensitivity differences caused by manufacturing discreteness, thereby reducing the risk of missed detection; Second, multi-channel fusion can improve the signal-to-noise ratio of slip characteristics, suppress false alarms caused by occasional interference, and enable the system to obtain stable and repeatable recognition results even in the low clamping force, small slip and early slip stages; Third, the sensitive area is designed as a rectangular structure with the long axis along the X direction, so that it can obtain a longer effective contact coverage and more sufficient channel response information in the clamping opening and closing direction, thereby enhancing the reliability and repeatability of slip detection in the X direction.

[0046] Furthermore, to adapt to different tissue types and operational tasks, the elastic response and frequency response bandwidth of the piezoresistive cantilever beam can be set by adjusting its geometric parameters such as length and thickness. The piezoresistive sensitivity and range can be changed by adjusting the ion implantation dose to meet the requirements of different soft tissues such as blood vessels and the digestive tract in terms of clamping force range and slip resolution. The sensor is preferably fabricated using standard silicon-based MEMS processes, including DRIE (Deep Reactive Ion Etching), ion implantation to form the piezoresistive layer, and metal interconnects. Temperature drift suppression and common-mode interference suppression are achieved through isothermal matching of the reference arm and an optional reference bridge, thereby realizing high-sensitivity, low-latency coordinated sensing of force and slip.

[0047] According to a second aspect of the present invention, a force-slip detection minimally invasive surgical robot is provided, comprising a robot body and an end effector for force-slip detection of the minimally invasive surgical robot connected to the robot body as described above.

[0048] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A force-slip detection end effector for a minimally invasive surgical robot, comprising a first clamp (1) and a second clamp (2), wherein one end of the first clamp (1) and the second clamp (2) is rotatably engaged, characterized in that, The clamping surfaces of the first clamp (1) and the second clamp (2) are provided with grooves for installing the flexible deformation layer (3) and the force-slip sensor (4), and the force-slip sensor (4) is close to the inner side of the groove; the flexible deformation layer (3) is provided with a first contact (8) on the side close to the force-slip sensor (4); with the direction from one end to the other of the first clamp (1) and the second clamp (2) as the longitudinal direction, the first contact (8) is arranged in a longitudinal and transverse manner, with three sets of first contact (8) arranged in the longitudinal direction, and four in each set; the first contact (8) and the piezoresistive cantilever beam (10) of the force-slip sensor (4) are arranged in a one-to-one correspondence; When the first clamp (1) and the second clamp (2) hold the object, the flexible deformation layer (3) deforms, causing the first contact point (8) to trigger the piezoresistive cantilever beam (10) of the force-slip sensor (4) to deform, so as to decouple the three-dimensional force information and slip information based on the deformation of the force-slip sensor (4).

2. The force-slip detection end effector for a minimally invasive surgical robot according to claim 1, characterized in that, The flexible deformable layer (3) has a positioning post (7) on the side near the force-slip sensor (4), and the force-slip sensor (4) has a positioning hole (9). The positioning post (7) and the positioning hole (9) cooperate to limit the position of the force-slip sensor (4) and the flexible deformable layer (3).

3. The force-slip detection end effector for a minimally invasive surgical robot according to claim 1, characterized in that, The flexible deformable layer (3) has second contacts evenly distributed on the side away from the force-slip sensor (4).

4. The force-slip detection end effector for a minimally invasive surgical robot according to claim 3, characterized in that, The second contact has a cylindrical structure.

5. The force-slip detection end effector for a minimally invasive surgical robot according to claim 1, characterized in that, The force-slip sensor (4) includes a substrate on which piezoresistive cantilever beams (10) are arranged in a one-to-one correspondence with the first contact (8) to form twelve detection units; each detection unit uses a piezoresistive cantilever beam (10) as a strain-sensitive arm resistor and three reference arm resistors to form a Wheatstone bridge.

6. The force-slip detection end effector for a minimally invasive surgical robot according to claim 1, characterized in that, The first contact (8) adopts an inverted cone or hemispherical structure.

7. A minimally invasive surgical robot for force-slip detection, characterized in that, The minimally invasive surgical robot end effector comprising a robot body and a force-slip detection device as described in any one of claims 1-6 connected to the robot body.

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