Manfredi, Luigi

English

Every year about two million new cases of colorectal cancer are diagnosed worldwide, with a mortality close to 50%. Screening and early detection are key to increase the five-year survival rate, which goes above 90% when the cancer is detected at stage 1 and drops below 10% at stage 4. Non-invasive screening, such as FIT (Faecal Immunochemical Test), is adopted in many national bowel screening programs to detect cancer at early stage. Colonoscopy remains the ultimate step to have an optical inspection of the colonic wall and to remove polyps, which may eventually become cancerous. However, this procedure is not well accepted by patients due to pain and discomfort. The pressure of the colonoscope against the colonic wall can damage the mucosa and, in some cases, cause perforation. It is a difficult procedure to learn, and training can take more than 4 years in the UK.This work presents a hybrid and low-cost control hardware including miniaturised valves, with linear actuators and piston-cylinder mechanisms to control a soft colonoscope. The proposed design combines a precise control of the fluid pressure and volumes in each chamber

University of Dundee Online Publications

                                                                    University of DundeeA Low-Cost Hybrid Compact Control Hardware for a Soft ColonoscopeManfredi, LuigiPublished in:GMM-Fb. 101: ACTUATOR 2022Publication date:2022Document VersionPeer reviewed versionLink to publication in Discovery Research PortalCitation for published version (APA):Manfredi, L. (2022). A Low-Cost Hybrid Compact Control Hardware for a Soft Colonoscope. In GMM-Fb. 101:ACTUATOR 2022: International Conference and Exhibition on New Actuator Systems and Applications (pp. 298-301). [77] GMM-Fachberichte.General rightsCopyright and moral rights for the publications made accessible in Discovery Research Portal are retained by the authors and/or othercopyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated withthese rights. • Users may download and print one copy of any publication from Discovery Research Portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain. • You may freely distribute the URL identifying the publication in the public portal.Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Download date: 16. Nov. 2022A Low-Cost Hybrid Compact Control Hardware for a Soft Colono-scope  Dr Luigi Manfredi, Division of Imaging Science and Technology, School of Medicine, University of Dundee, Dundee, UK, email: mail@luigimanfredi.com  Abstract Every year about two million new cases of colorectal cancer are diagnosed worldwide, with a mortality close to 50%. Screening and early detection are key to increase the five-year survival rate, which goes above 90% when the cancer is detected at stage 1 and drops below 10% at stage 4. Non-invasive screening, such as FIT (Faecal Immunochemical Test), is adopted in many national bowel screening programs to detect cancer at early stage. Colonoscopy remains the ultimate step to have an optical inspection of the colonic wall and to remove polyps, which may eventually become cancerous. However, this procedure is not well accepted by patients due to pain and discomfort. The pressure of the colonoscope against the colonic wall can damage the mucosa and, in some cases, cause perforation. It is a difficult procedure to learn, and training can take more than 4 years in the UK. This work presents a hybrid and low-cost control hardware including miniaturised valves, with linear actuators and piston-cylinder mechanisms to control a soft colonoscope. The proposed design combines a precise control of the fluid pressure and volumes in each chamber.  1 Introduction  Colorectal cancer causes 1.9M new cases per year world-wide with almost 900K death [1]. Early detection is key, with a five year survival rate above 90% at stage one and below 10% at stage four [2]. There are several non-invasive screenings tests, however colonoscopy is the only proce-dure with dual capability to screen the colonic mucosa and to remove polyps [3]. The first screening of the entire colon and polypectomy by using an electrosurgical snare was performed in 1969 [4]. Since then, colonoscopy has been the gold standard for colorectal cancer [5], [6]. Due to lim-itations of the current procedure, such as the difficult learn-ing process [7], discomfort for the patients, and in some cases, perforation of the colon [8], research institutes and industries are working on alternative, cost effective, and more efficient solutions. However, limited are the devices that have been granted CE mark or FDA approval. The de-signing of a medical device to screen the entire colon with on-board instrumentations has many challenges due to the slippery surface of the colonic mucosa and limited space inside the lumen [9]. Forces applied by the device for loco-motion are essential to reduce pain and discomfort as well as to avoid any damage to the colonic mucosa. Soft robot-ics, in particular fluidic soft devices, can provide a valuable solution due to the mechanical properties that make a de-vice intrinsically safe when interacting with human organs [10], [11],[12], [13], [14]. However, the elastic properties can cause instability issues, lack of precision in the control, and reduce the mechanical bandwidth. Instability can be related to the control strategy but also to the hardware that implements the control variable, such as pressure or vol-ume of the fluid inside the device. 1.1 State of the art The control of fluidic soft robots can have either on-board components or external components with tubes to inject the fluid in each chamber. The first robot with all the compo-nents on-board was presented by [15], with a chemical pressure generator for the activation of the pneumatic chambers. In a much bigger scale, a fully untethered quad-ruped robot with a length of 65cm and a weight of 5kg was designed with all the components on-board [16]. The air was generated by using an on-board electric pump and electric valves used to control the pressure inside each chamber. An autonomous soft fish with on-board control, valves, and a pressure regulator was designed to study bio-logical fishes [17]. A small and compact wireless pneumatic hardware was de-signed to control chamber pressures in a pneumatic soft ro-bot by using inlet and outlet valves, pressure sensors and a Bluetooth wireless communication [18], [19]. The control was implemented with a closed control loop at 1.5KHz. The hardware proposed in this work has been designed to control a soft colonoscope that applies low pressure against the colonic wall, together with an effective locomotion so-lution experimentally validated in a plastic phantom, to in-spect the large bowel [20].  1.2 Methods Pressure sensors are often used to control fluidic soft robots due to, in some designs, a linear relation between pressure and displacement [20]. This requires a loop to be closed at a frequency above 1KHz to avoid instability. The use of valves reduces the overall volume of the hardware since one source of fluid can be used to control several chambers. The pressure in each chamber can be implemented by using an inlet and outlet valve. When the control variable is the volume, instead, a piston-cylinder can be used. The piston compresses the fluid according to its displacement and in-ner diameter (bore). However, this architecture will in-crease the overall size of the hardware compared to one that uses valves and an external fluid supplier. The presented work describes a hardware that can be used to control a soft inchworm double balloon colonoscope by using a combination of piston-cylinder and valves. The hardware includes three linear actuators actuated by means of a piston-cylinder mechanism for each chamber, which uses a compact mechanical connection designed to reduce the overall space together with a low-cost stepper motor. By contrast, proportional valves are used to control the bal-loons. This hybrid solution has been proposed considering that the balloons must secure anchorage in different sec-tions of the colon (which can reach a diameter close to 80 mm [21]), hence they require a large volume of air for their activation. This would require the use of a large piston-cyl-inder hardware, which would increase the overall size of the control unit. Two valves, one inlet (IVi) and one outlet (OVi), are used to control the diameter of each balloon and to secure anchorage while keeping the pressure against the colonic wall low in order to reduce pain and discomfort. The hardware has been designed to control a soft inchworm colonoscope, which consists of two balloons connected by means of a three degrees of freedom (DOFs) soft pneu-matic actuator (SPA) [20]. 1.2.1 Control hardware The control hardware consists of two units. One wired unit to control three piston-cylinders (UN1), and the other one wireless to control the two balloons (UN2). The control ar-chitecture is shown in Figure 1. UN1 is dedicated to control the three DOFs SPA, while the UN2 to control the two bal-loons, with two additional DOFs, for a total five DOFs. UN2 design is reported in [18] In UN1, the piston-cylinder mechanism, PCi, i (i=1,2,3), is controlled by using a stepper motor with the volume Vi re-lated to the displacement of the piston. For simplicity this relationship is assumed to be directly proportional to the displacement dpi, Vi=K dpi. The mechanical design is shown in Figure 2. Each stepper motor is connected to a ball screw linear guide with a spool of 100mm. The actua-tor slide stoke guide is connected to a Festo pneumatic cyl-inder with a 25mm bore, and a 100mm stroke (DSNU-25-100-PPV-A), which is placed above the linear guide. The connection is made by using two rigid parts made from VeroClear (Tensile Strength 40 – 55 MPa (5,800 – 8,000 psi), Modulus of Elasticity 2,200 – 3,000 MPa (320,000 – 435,000 psi)) by using a 3D printed Stratasys Object30 Pro. Figure 1 Architecture of the design implemented in the control units connected to the three piston-cylinder mech-anisms to control the three chambers (C1, C2, C3) and the two balloons (B1, B2). Figure 2: CAD renders of the mechanical components to control volume in one chamber. Piston-cylinder hardware is shown in subfigure a), b), c), where a) is the front-view, b) top-view, and c) a prospective view. Par1is shown in sub-figures d), e), f), and Par2 is shown in sub-figures g), h), i). Figure 2 shows a CAD design of the part to control one chamber. This design reduces the overall length and weight of the hardware and makes it modular. One end of the cyl-inder is fixed to the slide stoke through Par1, (Sub figure 2-d), e), f)) while the piston is fix to the frame of the guide through Par2, (Sub figure 2-g), h), i)). A visual inspection of the mechanical connection does not show any defor-mation after an extensive use of the hardware. Each piston uses a 4mm push-fit connector to provide fluid to each chamber. A thread and a bolt in Par2 fix the piston and are used to precisely adjust the displacement of the piston. The internal volume is controlled by using dpi in the loop and a Proportional-Integrative (PI) controller. The use of stepper motors simplifies the implementation of the control of the position and speed of the piston, which is proportional to the input pulse frequency of the steps provided. The control of the stepper motors is implemented by using an Arduino Leonardo board together with low-cost stepper motor driver controllers (TB6600 4A 9-42V). The firmware is implemented in “C”, runs two tasks, defined as a low-level control (LLC1): Task1, data communication with an exter-nal console; Task2, implements three PIi controllers for the speed of the three steppers motors. The firmware receives data from an external console where the high-level control (HLC) is implemented in MATLAB® Simulink. The HLC executes the speed for each actuator and receives back from the LLC1 the position of each piston dpi. The speed is controlled by using a Microsoft® Xbox controller. UN2 is dedicated to control the pressure inside the two bal-loons. The firmware is implemented in “C” code in a 16 bits Microchip DSP (digital signal processor), which runs three parallel tasks in the LLC2: Task1, is dedicated to the data communication with an external console; Task2, im-plements the control of the pressure by using a PIDi and two proportional miniaturised valves, inlet and outlet. The HLC in the external console sends the pressure reference variable to be controlled inside each balloon.  The Microsoft® Xbox in the HLC facilitates the manoeu-vrability of the soft colonoscope and the implementation of more advanced locomotion strategies. The design of the UN1 has a modular design which allows to include additional hardware, if this is required, increas-ing the number of chambers to control. This will be limited by the number of digital inputs available to the Arduino board. A higher number of modules will reduce the control loop sample time due to the increase of data sent through the serial communication. 2 Conclusions A low-cost hybrid hardware to control a pneumatic soft de-vice, specifically a five DOFs inchworm soft colonoscope, has been presented. This work can control pressure and volume of fluid inside each chamber independently. The combination of pneumatic linear actuators and propor-tional pneumatic valves allows the implementation of mul-tiple control strategies. This can improve the precision and the implementation of different tasks, while reducing the stability problem related to the internal pressure as a single control variable. A HLC strategy can be implemented and validated. The components used for the development have been selected to be low-cost while having an effective con-trol solution. The use of a Microsoft® Xbox controller fa-cilitates the manoeuvrability of the device, and MATLAB® Simulink where the HLC is implemented, simplify the implementation and validation of different control strategies. Additional work can be done to improve the proposed de-sign. The use of stepper motors facilitates the LLC1 and reduces costs. However, the lack of on-board position sen-sors reduces the speed of the movement. To avoid missing steps in the control, the top speed is limited. The power consumption is high even if the stepper-motors are holding a fixed position; this is due to the driver selected for the control. Brushless or brushed motors together with encod-ers can improve the performance, however, produce an in-crease in costs and complications in the implementation of the LLC1. Pressure sensors can be used in the loop of the control of the volume of the fluid. This solution could be used to implement more advanced control strategies and to identify any issues in the controller like, for example, fluid leakage, or if an external force is applied.  This work focusses on the mechanical implementation and additional experiments are needed to identify the overall performance in terms of controllability and interaction with the external environment. 3 Literature [1] H. Sung et al., “Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries,” CA. Cancer J. Clin., vol. 0, no. 0, pp. 1–41, 2021, doi: 10.3322/caac.21660. [2] F. N. Van Erning et al., “Conditional survival for long-term colorectal cancer survivors in the Netherlands: Who do best?,” Eur. J. Cancer, vol. 50, no. 10, pp. 1731–1739, 2014, doi: 10.1016/j.ejca.2014.04.009. [3] M. Tepus and T. O. Yau, “Non-Invasive Colorectal Cancer Screening: An Overview,” Gastrointest. Tumors, vol. 7, no. 3, pp. 62–73, 2020, doi: 10.1159/000507701. [4] H. Shinya and W. Wolff, “Flexible colonoscopy,” Cancer, vol. 37, no. 1 S, pp. 462–470, 1976, doi: 10.1002/1097-0142(197601)37:1+<462::AID-CNCR2820370710>3.0.CO;2-7. [5] J. Nee, R. Z. Chippendale, and J. D. Feuerstein, “Screening for Colon Cancer in Older Adults: Risks, Benefits, and When to Stop,” Mayo Clin. Proc., vol. 95, no. 1, pp. 184–196, 2020, doi: 10.1016/j.mayocp.2019.02.021. [6] H. Brenner, C. Stock, and M. Hoffmeister, “Effect of screening sigmoidoscopy and screening colonoscopy on colorectal cancer incidence and mortality: Systematic review and meta-analysis of randomised controlled trials and observational studies,” BMJ, vol. 348, no. April, pp. 1–12, 2014, doi: 10.1136/bmj.g2467. [7] K. Siau et al., “Certification of UK gastrointestinal endoscopists and variations between trainee specialties: results from the JETS e-portfolio,” Endosc. Int. Open, vol. 07, no. 04, pp. E551–E560, 2019, doi: 10.1055/a-0839-4476. [8] C. R. Morris, I. M. Harvey, W. S. L. Stebbings, and A. R. Hart, “Incidence of perforated diverticulitis and risk factors for death in a UK population,” Br. J. Surg., vol. 95, no. 7, pp. 876–881, 2008, doi: 10.1002/bjs.6226. [9] L. Manfredi, “Endorobots for Colonoscopy : Design Challenges and Available Technologies,” vol. 8, no. July, pp. 1–10, 2021, doi: 10.3389/frobt.2021.705454. [10] D. Rus and M. T. Tolley, “Design, fabrication and control of soft robots,” Nature, vol. 521, no. 7553, pp. 467–475, 2015, doi: 10.1038/nature14543. [11] C. Laschi, B. Mazzolai, and M. Cianchetti, “Soft robotics: Technologies and systems pushing the boundaries of robot abilities,” Sci. Robot., vol. 1, no. 1, pp. 1–11, 2016, doi: 10.1126/scirobotics.aah3690. [12] L. Manfredi, F. Putzu, S. Guler, Y. Huan, and A. Cuschieri, “4 DOFs hollow soft pneumatic actuator–hose,” Mater. Res. Express, vol. 6, no. 4, 2019, doi: 10.1088/2053-1591/aaebea. [13] L. Manfredi, L. Yue, J. Zhang, and A. Cuschieri, “A 4 DOFs variable stiffness soft module,” 2018 IEEE Int. Conf. Soft Robot. RoboSoft 2018, pp. 94–99, 2018, doi: 10.1109/ROBOSOFT.2018.8404903. [14] L. Manfredi, L. Yue, and A. Cuschieri, “A 3 DOFs mini variable stiffness soft pneumatic actuator,” in ACTUATOR 2018 - 16th International Conference and Exhibition on New Actuators and Drive Systems, Conference Proceedings, 2018, no. June, pp. 169–172. [15] M. Wehner et al., “An integrated design and fabrication strategy for entirely soft, autonomous robots,” Nat. Publ. Gr., vol. 536, no. 7617, pp. 451–455, 2016, doi: 10.1038/nature19100. [16] T. Michael et al., “A Resilient , Untethered Soft Robot The Harvard community has made this article openly available . Please share how this access benefits you . Your story matters . Citation Accessed,” 2016, doi: 10.1089/soro.2014.0008. [17] M. Using, F. Elastomer, A. D. Marchese, C. D. Onal, and D. Rus, “Autonomous Soft Robotic Fish Capable of Escape,” vol. 1, no. 1, pp. 75–87, 2014, doi: 10.1089/soro.2013.0009. [18] L. Manfredi and A. Cuschieri, “A wireless compact control unit (WiCCU) for untethered pneumatic soft robots,” in RoboSoft 2019 - 2019 IEEE International Conference on Soft Robotics, 2019, pp. 31–36, doi: 10.1109/ROBOSOFT.2019.8722788. [19] L. Manfredi, “A compact control unit for a pneumatic soft colonoscope,” in GMM-Fachberichte, 2021, vol. 2021-February, no. 98, pp. 273–276. [20] L. Manfredi, E. Capoccia, G. Ciuti, and A. Cuschieri, “A Soft Pneumatic Inchworm Double balloon (SPID) for colonoscopy,” Sci. Rep., vol. 9, no. 1, pp. 1–9, 2019, doi: 10.1038/s41598-019-47320-3. [21] A. Alazmani, A. Hood, D. Jayne, A. Neville, and P. Culmer, “Quantitative assessment of colorectal morphology: Implications for robotic colonoscopy,” Med. Eng. Phys., vol. 38, no. 2, pp. 148–154, 2016, doi: 10.1016/j.medengphy.2015.11.018.  

A Low-Cost Hybrid Compact Control Hardware for a Soft Colonoscope

                                                                    University of DundeeA Low-Cost Hybrid Compact Control Hardware for a Soft ColonoscopeManfredi, LuigiPublished in:GMM-Fb. 101: ACTUATOR 2022Publication date:2022Document VersionPeer reviewed versionLink to publication in Discovery Research PortalCitation for published version (APA):Manfredi, L. (2022). A Low-Cost Hybrid Compact Control Hardware for a Soft Colonoscope. In GMM-Fb. 101:ACTUATOR 2022: International Conference and Exhibition on New Actuator Systems and Applications (pp. 298-301). [77] GMM-Fachberichte.General rightsCopyright and moral rights for the publications made accessible in Discovery Research Portal are retained by the authors and/or othercopyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated withthese rights. • Users may download and print one copy of any publication from Discovery Research Portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain. • You may freely distribute the URL identifying the publication in the public portal.Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Download date: 19. Apr. 2023A Low-Cost Hybrid Compact Control Hardware for a Soft Colono-scope  Dr Luigi Manfredi, Division of Imaging Science and Technology, School of Medicine, University of Dundee, Dundee, UK, email: mail@luigimanfredi.com  Abstract Every year about two million new cases of colorectal cancer are diagnosed worldwide, with a mortality close to 50%. Screening and early detection are key to increase the five-year survival rate, which goes above 90% when the cancer is detected at stage 1 and drops below 10% at stage 4. Non-invasive screening, such as FIT (Faecal Immunochemical Test), is adopted in many national bowel screening programs to detect cancer at early stage. Colonoscopy remains the ultimate step to have an optical inspection of the colonic wall and to remove polyps, which may eventually become cancerous. However, this procedure is not well accepted by patients due to pain and discomfort. The pressure of the colonoscope against the colonic wall can damage the mucosa and, in some cases, cause perforation. It is a difficult procedure to learn, and training can take more than 4 years in the UK. This work presents a hybrid and low-cost control hardware including miniaturised valves, with linear actuators and piston-cylinder mechanisms to control a soft colonoscope. The proposed design combines a precise control of the fluid pressure and volumes in each chamber.  1 Introduction  Colorectal cancer causes 1.9M new cases per year world-wide with almost 900K death [1]. Early detection is key, with a five year survival rate above 90% at stage one and below 10% at stage four [2]. There are several non-invasive screenings tests, however colonoscopy is the only proce-dure with dual capability to screen the colonic mucosa and to remove polyps [3]. The first screening of the entire colon and polypectomy by using an electrosurgical snare was performed in 1969 [4]. Since then, colonoscopy has been the gold standard for colorectal cancer [5], [6]. Due to lim-itations of the current procedure, such as the difficult learn-ing process [7], discomfort for the patients, and in some cases, perforation of the colon [8], research institutes and industries are working on alternative, cost effective, and more efficient solutions. However, limited are the devices that have been granted CE mark or FDA approval. The de-signing of a medical device to screen the entire colon with on-board instrumentations has many challenges due to the slippery surface of the colonic mucosa and limited space inside the lumen [9]. Forces applied by the device for loco-motion are essential to reduce pain and discomfort as well as to avoid any damage to the colonic mucosa. Soft robot-ics, in particular fluidic soft devices, can provide a valuable solution due to the mechanical properties that make a de-vice intrinsically safe when interacting with human organs [10], [11],[12], [13], [14]. However, the elastic properties can cause instability issues, lack of precision in the control, and reduce the mechanical bandwidth. Instability can be related to the control strategy but also to the hardware that implements the control variable, such as pressure or vol-ume of the fluid inside the device. 1.1 State of the art The control of fluidic soft robots can have either on-board components or external components with tubes to inject the fluid in each chamber. The first robot with all the compo-nents on-board was presented by [15], with a chemical pressure generator for the activation of the pneumatic chambers. In a much bigger scale, a fully untethered quad-ruped robot with a length of 65cm and a weight of 5kg was designed with all the components on-board [16]. The air was generated by using an on-board electric pump and electric valves used to control the pressure inside each chamber. An autonomous soft fish with on-board control, valves, and a pressure regulator was designed to study bio-logical fishes [17]. A small and compact wireless pneumatic hardware was de-signed to control chamber pressures in a pneumatic soft ro-bot by using inlet and outlet valves, pressure sensors and a Bluetooth wireless communication [18], [19]. The control was implemented with a closed control loop at 1.5KHz. The hardware proposed in this work has been designed to control a soft colonoscope that applies low pressure against the colonic wall, together with an effective locomotion so-lution experimentally validated in a plastic phantom, to in-spect the large bowel [20].  1.2 Methods Pressure sensors are often used to control fluidic soft robots due to, in some designs, a linear relation between pressure and displacement [20]. This requires a loop to be closed at a frequency above 1KHz to avoid instability. The use of valves reduces the overall volume of the hardware since one source of fluid can be used to control several chambers. The pressure in each chamber can be implemented by using an inlet and outlet valve. When the control variable is the volume, instead, a piston-cylinder can be used. The piston compresses the fluid according to its displacement and in-ner diameter (bore). However, this architecture will in-crease the overall size of the hardware compared to one that uses valves and an external fluid supplier. The presented work describes a hardware that can be used to control a soft inchworm double balloon colonoscope by using a combination of piston-cylinder and valves. The hardware includes three linear actuators actuated by means of a piston-cylinder mechanism for each chamber, which uses a compact mechanical connection designed to reduce the overall space together with a low-cost stepper motor. By contrast, proportional valves are used to control the bal-loons. This hybrid solution has been proposed considering that the balloons must secure anchorage in different sec-tions of the colon (which can reach a diameter close to 80 mm [21]), hence they require a large volume of air for their activation. This would require the use of a large piston-cyl-inder hardware, which would increase the overall size of the control unit. Two valves, one inlet (IVi) and one outlet (OVi), are used to control the diameter of each balloon and to secure anchorage while keeping the pressure against the colonic wall low in order to reduce pain and discomfort. The hardware has been designed to control a soft inchworm colonoscope, which consists of two balloons connected by means of a three degrees of freedom (DOFs) soft pneu-matic actuator (SPA) [20]. 1.2.1 Control hardware The control hardware consists of two units. One wired unit to control three piston-cylinders (UN1), and the other one wireless to control the two balloons (UN2). The control ar-chitecture is shown in Figure 1. UN1 is dedicated to control the three DOFs SPA, while the UN2 to control the two bal-loons, with two additional DOFs, for a total five DOFs. UN2 design is reported in [18] In UN1, the piston-cylinder mechanism, PCi, i (i=1,2,3), is controlled by using a stepper motor with the volume Vi re-lated to the displacement of the piston. For simplicity this relationship is assumed to be directly proportional to the displacement dpi, Vi=K dpi. The mechanical design is shown in Figure 2. Each stepper motor is connected to a ball screw linear guide with a spool of 100mm. The actua-tor slide stoke guide is connected to a Festo pneumatic cyl-inder with a 25mm bore, and a 100mm stroke (DSNU-25-100-PPV-A), which is placed above the linear guide. The connection is made by using two rigid parts made from VeroClear (Tensile Strength 40 – 55 MPa (5,800 – 8,000 psi), Modulus of Elasticity 2,200 – 3,000 MPa (320,000 – 435,000 psi)) by using a 3D printed Stratasys Object30 Pro. Figure 1 Architecture of the design implemented in the control units connected to the three piston-cylinder mech-anisms to control the three chambers (C1, C2, C3) and the two balloons (B1, B2). Figure 2: CAD renders of the mechanical components to control volume in one chamber. Piston-cylinder hardware is shown in subfigure a), b), c), where a) is the front-view, b) top-view, and c) a prospective view. Par1is shown in sub-figures d), e), f), and Par2 is shown in sub-figures g), h), i). Figure 2 shows a CAD design of the part to control one chamber. This design reduces the overall length and weight of the hardware and makes it modular. One end of the cyl-inder is fixed to the slide stoke through Par1, (Sub figure 2-d), e), f)) while the piston is fix to the frame of the guide through Par2, (Sub figure 2-g), h), i)). A visual inspection of the mechanical connection does not show any defor-mation after an extensive use of the hardware. Each piston uses a 4mm push-fit connector to provide fluid to each chamber. A thread and a bolt in Par2 fix the piston and are used to precisely adjust the displacement of the piston. The internal volume is controlled by using dpi in the loop and a Proportional-Integrative (PI) controller. The use of stepper motors simplifies the implementation of the control of the position and speed of the piston, which is proportional to the input pulse frequency of the steps provided. The control of the stepper motors is implemented by using an Arduino Leonardo board together with low-cost stepper motor driver controllers (TB6600 4A 9-42V). The firmware is implemented in “C”, runs two tasks, defined as a low-level control (LLC1): Task1, data communication with an exter-nal console; Task2, implements three PIi controllers for the speed of the three steppers motors. The firmware receives data from an external console where the high-level control (HLC) is implemented in MATLAB® Simulink. The HLC executes the speed for each actuator and receives back from the LLC1 the position of each piston dpi. The speed is controlled by using a Microsoft® Xbox controller. UN2 is dedicated to control the pressure inside the two bal-loons. The firmware is implemented in “C” code in a 16 bits Microchip DSP (digital signal processor), which runs three parallel tasks in the LLC2: Task1, is dedicated to the data communication with an external console; Task2, im-plements the control of the pressure by using a PIDi and two proportional miniaturised valves, inlet and outlet. The HLC in the external console sends the pressure reference variable to be controlled inside each balloon.  The Microsoft® Xbox in the HLC facilitates the manoeu-vrability of the soft colonoscope and the implementation of more advanced locomotion strategies. The design of the UN1 has a modular design which allows to include additional hardware, if this is required, increas-ing the number of chambers to control. This will be limited by the number of digital inputs available to the Arduino board. A higher number of modules will reduce the control loop sample time due to the increase of data sent through the serial communication. 2 Conclusions A low-cost hybrid hardware to control a pneumatic soft de-vice, specifically a five DOFs inchworm soft colonoscope, has been presented. This work can control pressure and volume of fluid inside each chamber independently. The combination of pneumatic linear actuators and propor-tional pneumatic valves allows the implementation of mul-tiple control strategies. This can improve the precision and the implementation of different tasks, while reducing the stability problem related to the internal pressure as a single control variable. A HLC strategy can be implemented and validated. The components used for the development have been selected to be low-cost while having an effective con-trol solution. The use of a Microsoft® Xbox controller fa-cilitates the manoeuvrability of the device, and MATLAB® Simulink where the HLC is implemented, simplify the implementation and validation of different control strategies. Additional work can be done to improve the proposed de-sign. The use of stepper motors facilitates the LLC1 and reduces costs. However, the lack of on-board position sen-sors reduces the speed of the movement. To avoid missing steps in the control, the top speed is limited. The power consumption is high even if the stepper-motors are holding a fixed position; this is due to the driver selected for the control. Brushless or brushed motors together with encod-ers can improve the performance, however, produce an in-crease in costs and complications in the implementation of the LLC1. Pressure sensors can be used in the loop of the control of the volume of the fluid. This solution could be used to implement more advanced control strategies and to identify any issues in the controller like, for example, fluid leakage, or if an external force is applied.  This work focusses on the mechanical implementation and additional experiments are needed to identify the overall performance in terms of controllability and interaction with the external environment. 3 Literature [1] H. Sung et al., “Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries,” CA. Cancer J. Clin., vol. 0, no. 0, pp. 1–41, 2021, doi: 10.3322/caac.21660. [2] F. N. Van Erning et al., “Conditional survival for long-term colorectal cancer survivors in the Netherlands: Who do best?,” Eur. J. Cancer, vol. 50, no. 10, pp. 1731–1739, 2014, doi: 10.1016/j.ejca.2014.04.009. [3] M. Tepus and T. O. Yau, “Non-Invasive Colorectal Cancer Screening: An Overview,” Gastrointest. Tumors, vol. 7, no. 3, pp. 62–73, 2020, doi: 10.1159/000507701. [4] H. Shinya and W. Wolff, “Flexible colonoscopy,” Cancer, vol. 37, no. 1 S, pp. 462–470, 1976, doi: 10.1002/1097-0142(197601)37:1+<462::AID-CNCR2820370710>3.0.CO;2-7. [5] J. Nee, R. Z. Chippendale, and J. D. Feuerstein, “Screening for Colon Cancer in Older Adults: Risks, Benefits, and When to Stop,” Mayo Clin. Proc., vol. 95, no. 1, pp. 184–196, 2020, doi: 10.1016/j.mayocp.2019.02.021. [6] H. Brenner, C. Stock, and M. Hoffmeister, “Effect of screening sigmoidoscopy and screening colonoscopy on colorectal cancer incidence and mortality: Systematic review and meta-analysis of randomised controlled trials and observational studies,” BMJ, vol. 348, no. April, pp. 1–12, 2014, doi: 10.1136/bmj.g2467. [7] K. Siau et al., “Certification of UK gastrointestinal endoscopists and variations between trainee specialties: results from the JETS e-portfolio,” Endosc. Int. Open, vol. 07, no. 04, pp. E551–E560, 2019, doi: 10.1055/a-0839-4476. [8] C. R. Morris, I. M. Harvey, W. S. L. Stebbings, and A. R. Hart, “Incidence of perforated diverticulitis and risk factors for death in a UK population,” Br. J. Surg., vol. 95, no. 7, pp. 876–881, 2008, doi: 10.1002/bjs.6226. [9] L. Manfredi, “Endorobots for Colonoscopy : Design Challenges and Available Technologies,” vol. 8, no. July, pp. 1–10, 2021, doi: 10.3389/frobt.2021.705454. [10] D. Rus and M. T. Tolley, “Design, fabrication and control of soft robots,” Nature, vol. 521, no. 7553, pp. 467–475, 2015, doi: 10.1038/nature14543. [11] C. Laschi, B. Mazzolai, and M. Cianchetti, “Soft robotics: Technologies and systems pushing the boundaries of robot abilities,” Sci. Robot., vol. 1, no. 1, pp. 1–11, 2016, doi: 10.1126/scirobotics.aah3690. [12] L. Manfredi, F. Putzu, S. Guler, Y. Huan, and A. Cuschieri, “4 DOFs hollow soft pneumatic actuator–hose,” Mater. Res. Express, vol. 6, no. 4, 2019, doi: 10.1088/2053-1591/aaebea. [13] L. Manfredi, L. Yue, J. Zhang, and A. Cuschieri, “A 4 DOFs variable stiffness soft module,” 2018 IEEE Int. Conf. Soft Robot. RoboSoft 2018, pp. 94–99, 2018, doi: 10.1109/ROBOSOFT.2018.8404903. [14] L. Manfredi, L. Yue, and A. Cuschieri, “A 3 DOFs mini variable stiffness soft pneumatic actuator,” in ACTUATOR 2018 - 16th International Conference and Exhibition on New Actuators and Drive Systems, Conference Proceedings, 2018, no. June, pp. 169–172. [15] M. Wehner et al., “An integrated design and fabrication strategy for entirely soft, autonomous robots,” Nat. Publ. Gr., vol. 536, no. 7617, pp. 451–455, 2016, doi: 10.1038/nature19100. [16] T. Michael et al., “A Resilient , Untethered Soft Robot The Harvard community has made this article openly available . Please share how this access benefits you . Your story matters . Citation Accessed,” 2016, doi: 10.1089/soro.2014.0008. [17] M. Using, F. Elastomer, A. D. Marchese, C. D. Onal, and D. Rus, “Autonomous Soft Robotic Fish Capable of Escape,” vol. 1, no. 1, pp. 75–87, 2014, doi: 10.1089/soro.2013.0009. [18] L. Manfredi and A. Cuschieri, “A wireless compact control unit (WiCCU) for untethered pneumatic soft robots,” in RoboSoft 2019 - 2019 IEEE International Conference on Soft Robotics, 2019, pp. 31–36, doi: 10.1109/ROBOSOFT.2019.8722788. [19] L. Manfredi, “A compact control unit for a pneumatic soft colonoscope,” in GMM-Fachberichte, 2021, vol. 2021-February, no. 98, pp. 273–276. [20] L. Manfredi, E. Capoccia, G. Ciuti, and A. Cuschieri, “A Soft Pneumatic Inchworm Double balloon (SPID) for colonoscopy,” Sci. Rep., vol. 9, no. 1, pp. 1–9, 2019, doi: 10.1038/s41598-019-47320-3. [21] A. Alazmani, A. Hood, D. Jayne, A. Neville, and P. Culmer, “Quantitative assessment of colorectal morphology: Implications for robotic colonoscopy,” Med. Eng. Phys., vol. 38, no. 2, pp. 148–154, 2016, doi: 10.1016/j.medengphy.2015.11.018.  

https://discovery.dundee.ac.uk/files/88173677/Actuator_2020_R13.pdf

A Low-Cost Hybrid Compact Control Hardware for a Soft Colonoscope

Abstract

Similar works

Full text

Available Versions

University of Dundee Online Publications

University of Dundee Online Publications