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Min Li

XI'AN JIAO TONG UNIVERSITY, School of Mechanical Engineering, Faculty Member

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Min Li received her B.S. Degree in Mechanical Engineering from Northwest A&F University, China in 2007. She received her M.Sc. degree in Agricultural Mechanization Engineering from the same university in 2010. She was awarded the Ph.D. degree in Robotics at King’s College London in 2014. The project was about haptic feedback for minimally invasive surgery. She is currently working in the School of Mechanical Engineering in Xi'an Jiaotong University China.
Supervisors: Professor Guanghua Xu, Professor Kaspar Althoefer, and Professor Lakmal Seneviratne

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Papers by Min Li

Multi-fingered haptic palpation using pneumatic feedback actuators

Sensors and Actuators A: Physical, 2014

This paper proposes a multi-fingered palpation method which employs pneumatic haptic feedback act... more This paper proposes a multi-fingered palpation method which employs pneumatic haptic feedback actuators allowing users to experience haptic sensations at multiple fingers while carrying out remote soft tissue palpation. Pneumatic actuators are used to vary the stress on the user's fingertips in accordance with the tissue stiffness, experienced during manual palpation. The proposed method reduces actuator elements compared to tactile actuators and provides more information than single-point force feedback. The results of our finite element analysis have proven that our pneumatic haptic feedback device can recreate the contact stress between fingertip and soft tissue during palpation. The accuracy (96.8% vs. 93.3%) and time-efficiency (4.6 s vs. 8.3 s) advantages of using three-fingered over single-fingered palpation have been confirmed in our user study results of stiffness levels discrimination. Relatively good tumor detection sensitivities have been demonstrated by the palpation user study which has showed a direct correlation between tumor size and detection sensitivity and has further proven the efficiency of the proposed actuator and multi-fingered palpation method for tumor detection in palpation simulation.

Haptics for Multi-fingered Palpation

by SHAN LUO, Thrishantha Nanayakkara, and Min Li

2013 IEEE International Conference on Systems, Man, and Cybernetics, 2013

Evaluation of Pseudo-Haptic Interactions with Soft Objects in Virtual Environments

by Min Li, SHAN LUO, and Helge A Wurdemann

This paper proposes a pseudo-haptic feedback method conveying simulated soft surface stiffness in... more This paper proposes a pseudo-haptic feedback method conveying simulated soft surface stiffness information through a visual interface. The method exploits a combination of two feedback techniques, namely visual feedback of soft surface deformation and control of the indenter avatar speed, to convey stiffness information of a simulated surface of a soft object in virtual environments. The proposed method was effective in distinguishing different sizes of virtual hard nodules integrated into the simulated soft bodies. To further improve the interactive experience, the approach was extended creating a multi-point pseudo-haptic feedback system. A comparison with regards to (a) nodule detection sensitivity and (b) elapsed time as performance indicators in hard nodule detection experiments to a tablet computer incorporating vibration feedback was conducted. The multi-point pseudo-haptic interaction is shown to be more time-efficient than the single-point pseudo-haptic interaction. It is noted that multi-point pseudo-haptic feedback performs similarly well when compared to a vibration based feedback method based on both performance measures elapsed time and nod-ule detection sensitivity. This proves that the proposed method can be used to convey detailed haptic information for virtual environmental tasks, even subtle ones, using either a computer mouse or a pressure sensitive device as an input device. This pseudo-haptic feedback method provides an opportunity for low-cost simulation of objects with soft surfaces and hard inclusions, as, for example, occurring in ever more realistic video games with increasing emphasis on interaction with the physical environment and minimally inva-sive surgery in the form of soft tissue organs with embedded cancer nodules. Hence, the method can be used in many low-budget applications where haptic sensation is required, such as surgeon training or video games, either using desktop computers or portable devices, showing reasonably high fidelity in conveying stiffness perception to the user.

Macrobend optical sensing for pose measurement in soft robot arms

by Min Li and Tommaso Ranzani

This paper introduces a pose-sensing system for soft robot arms integrating a set of macrobend st... more This paper introduces a pose-sensing system for soft robot arms integrating a set of macrobend stretch sensors. The macrobend sensory design in this study consists of optical ﬁbres and is based on the notion that bending an optical ﬁbre modulates the intensity of the light transmitted through the ﬁbre. This sensing method is capable of measuring bending, elongation and compression in soft continuum robots and is also applicable to wearable sensing technologies, e.g. pose sensing in the wrist joint of a human hand. In our arrangement, applied to a cylindrical soft robot arm, the optical ﬁbres for macrobend sensing originate from the base, extend to the tip of the arm, and then loop back to the base. The connectors that link the ﬁbres to the necessary opto-electronics are all placed at the base of the arm, resulting in a simpliﬁed overall design. The ability of this custom macrobend stretch sensor to ﬂexibly adapt its conﬁguration allows preserving the inherent softness and compliance of the robot which it is installed on. The macrobend sensing system is immune to electrical noise and magnetic ﬁelds, is safe (because no electricity is needed at the sensing site), and is suitable for modular implementation in multi-link soft continuum robotic arms. The measurable light outputs of the proposed stretch sensor vary due to bend-induced light attenuation (macrobend loss), which is a function of the ﬁbre bend radius as well as the number of repeated turns. The experimental study conducted as part of this research revealed that the chosen bend radius has a far greater impact on the measured light intensity values than the number of turns (if greater than ﬁve). Taking into account that the bend radius is the only signiﬁcantly inﬂuencing design parameter, the macrobend stretch sensors were developed to create a practical solution to the pose sensing in soft continuum robot arms. Henceforward, the proposed sensing design was benchmarked against an electromagnetic tracking system (NDI Aurora) for validation.

The Study of Object-Oriented Motor Imagery Based on EEG Suppression

by Min Li and Jun Xie

Motorimageryisaconventionalmethodforbraincomputerinterfaceandmotorlearning.To avoidthegreatindivi... more Motorimageryisaconventionalmethodforbraincomputerinterfaceandmotorlearning.To avoidthegreatindividualdifferenceofthemotorimageryability,object-orientedmotor imagery wasapplied,andtheeffectswerestudied.Kinestheticmotorimagery andvisual observationwereadministeredto15healthyvolunteers.TheEEGduringcue-basedsimple imagery (SI),object-orientedmotorimagery (OI), non-object-orientedmotorimagery (NI) andvisualobservation(VO) wasrecorded.StudyresultsshowedthatOIandNIpresented significantcontralateralsuppressioninmurhythm(p<0.05).Besides,OIexhibitedsignificantcontralateral suppressioninbetarhythm(p<0.05).Whilenosignificantmuorbeta contralateralsuppressioncouldbefoundduring VOorSI(p>0.05).ComparedwithNI,OI showedsignificantdifference(p<0.05)inmurhythmandweaksignificantdifference (p= 0.0612)inbetarhythmoverthecontralateralhemisphere.Theabilityofmotorimagerycan bereflectedbythesuppressiondegreeofmuandbetafrequencieswhicharethemotor relatedrhythms.Thus,greaterenhancementofactivationinmirrorneuronsystemis involvedinresponsetoobject-orientedmotorimagery.Theobject-orientedmotorimagery isfavorableforimprovementofmotorimageryability.

Measuring Cervical Vertebra Movements using Kinect Sensor

by Min Li and Jun Xie

—The incidence of cervical vertebra spondylosis is increasing with the pace of life while there i... more —The incidence of cervical vertebra spondylosis is increasing with the pace of life while there is no high-efficient measurement method. This study proposed a non-contact, high-efficient, and high-precisionmethod measuring the cervical vertebra activities which obtains the cervical vertebra activities by combining the function of skeletal tracking and face tracking. A comparison study between the proposed and traditional methods has been conducted here. Statistics shows that the efficiency of the proposed measurement method at least is 6 times faster than modified square shaped goniometers that is the represent of traditional measurement, and it's angular error in average is 0.35°. Moreover, the proposed measuring method has been tested in hospital clinical environment and the results show that the proposed method can be used easily and have little interference.

An EEG-driven Lower Limb Rehabilitation Training System for Active and Passive Co-stimulation

by Min Li, Jun Xie, and Wei Pei

— With the advent of an aging society, stroke makes a heavy burden for our society. Stroke can da... more — With the advent of an aging society, stroke makes a heavy burden for our society. Stroke can damage the motor and sensory neural system and block the closed loop between the brain and the body. Due to the neural plasticity, this closed loop can be rebuilt through training. Users' actively engagement can help expedite functional recovery. Therefore, we propose an EEG-driven Lower Limb Rehabilitation Training System (LLRTS) that can achieve Active and Passive Co-stimulation (APC). Virtual Reality (VR), BCI and robot are introduced into the system. When users have motor intentions, this system could automatically support corresponding visual and somatic sensory feedback. That is to say active and passive stimulations are controlled by user's mind. This paper reports the idea and construction of this rehabilitation system. Preliminary experimental results support the concept.

Evaluating Manual Palpation Trajectory Patterns in Tele-manipulation for Soft Tissue Examination

by Jelizaveta Konstantinova and Min Li

2013 IEEE International Conference on Systems, Man, and Cybernetics, 2013

Robot-assisted minimal invasive surgery made it possible to improve the quality of surgical proce... more Robot-assisted minimal invasive surgery made it possible to improve the quality of surgical procedures and to enhance clinical outcomes. However, the need to palpate soft tissue organs with the aim to localize potential sites of abnormalities in real time has been recognized. For this work, ten subjects were recruited to perform a remote palpation procedure on a silicone phantom utilizing a tele-manipulation setup, to study their behavior when remotely palpating soft tissue. The stiffness values acquired during the remote palpation of a silicone phantom were transferred to the subjects by means of haptic and visual feedback. Participating subjects were asked to detect hard nodules in the silicone tissue using two distinct strategies: a) randomly chosen movements, and b) trajectory pattern, based on manual palpation techniques for clinical breast examination. We have compared relevant parameters, defining patterns observed during manual palpation, with the counterpart patterns occurring during remote palpation. The results show the effectiveness of applying palpation trajectory pattern used during manual soft tissue examination to tele-manipulation palpation.

Behavioral Characteristics of Manual Palpation to Localize Hard Nodules in Soft Tissues

by Kaspar Althoefer, Thrishantha Nanayakkara, Gautam Mehra, Jelizaveta Konstantinova, and Min Li

IEEE Transactions on Biomedical Engineering, 2000

Improving the effectiveness of artificial tactile sensors for soft tissue examination and tumor l... more Improving the effectiveness of artificial tactile sensors for soft tissue examination and tumor localization is a pressing need in robot-assisted minimally invasive surgery. Despite the availability of tactile probes, guidelines for optimal palpation behavior that best exploit soft tissue properties are not available as yet. Simulations on soft-tissue palpation show that particular stress-velocity patterns during tissue probing lead to constructive dynamic interactions between the probe and the tissue, enhancing the detection and localization of hard nodules. To the best knowledge of the authors, this is the first attempt to methodically evaluate the hypothesis that specific human palpation behaviors (defined by the fingers' velocity, trajectory and exerted force) directly influence the diagnosis of soft tissue organs. Here, we use simulation studies involving human participants to establish open hypotheses on the interaction and influence of relevant behavioral palpation variables, such as finger trajectory, its velocity, and force exerted by fingers on the accuracy of detecting embedded nodules. We validate this hypothesis through finite element analysis and the investigation of palpation strategies used by humans during straight unidirectional examination to detect hard nodules inside silicone phantoms and ex-vivo porcine organs. Thus, we conclude that the palpation strategy plays an important role during soft tissue examination. Our findings allow us, for the first time, to derive palpation behavior guidelines suitable for the design of controllers of palpation robots.

Force-velocity modulation strategies for soft tissue examination

by Jelizaveta Konstantinova, Thrishantha Nanayakkara, and Min Li

2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013

Advanced tactile tools in minimally invasive surgery have become a pressing need in order to redu... more Advanced tactile tools in minimally invasive surgery have become a pressing need in order to reduce time and improve accuracy in localizing potential tissue abnormalities. In this regard, one of the main challenges is to be able to estimate tissue parameters in real time. In palpation, tactile information felt at a given location is identified by the viscoelastic dynamics of the neighboring tissue. Due to this reason the tissue examination behavior and the distribution of viscoelastic parameters in tissue should be considered in conjunction. This paper investigates the salient features of palpation behavior on soft tissue determining the effectiveness of localizing hard nodules. Experimental studies involving human participants, and validation tests using finite element simulations and a tele-manipulator, were carried out. Two distinctive tissue examination strategies in force-velocity modulation for the given properties of target tissue were found. Experimental results suggest that force-velocity modulations during continuous path measurements are playing an important role in the process of mechanical soft tissue examination. These behavioral insights, validated by detailed numerical models and robotic experimentations shed light on future designs of optimal robotic palpation.

Palpation Strategies for Artificial Soft Tissue Examination

by Kaspar Althoefer, Thrishantha Nanayakkara, Min Li, and Jelizaveta Konstantinova

This paper presents studies developed to understand the need of the specific behavioral strategie... more This paper presents studies developed to understand the need of the specific behavioral strategies during artificial tactile examination of soft tissues for robot-assisted minimally invasive surgery. Conventional manual palpation techniques are studied to understand the desired patterns that should be applied using intra-operative tactile probes. In addition the telemanipulation studies are carried out. Our results demonstrate the importance of application of specific palpation behavior during artificial tactile examination.

Real-time visual stiffness feedback for soft tissue palpation in a telemanipulation environment

by Jelizaveta Konstantinova and Min Li

Using visual cues to enhance haptic feedback for palpation on virtual model of soft tissue

by Helge A Wurdemann, Thrishantha Nanayakkara, Lakmal D. Seneviratne, Emanuele Lindo Secco, Jelizaveta Konstantinova, Min Li, Kaspar Althoefer, Prokar Dasgupta, and Allen Jiang

This paper explores methods that make use of visual cues aimed at generating actual haptic sensat... more This paper explores methods that make use of visual cues aimed at generating actual haptic sensation to the user, namely pseudo-haptics. We propose a new pseudo-haptic feedback-based method capable of conveying 3D haptic information and combining visual haptics with force feedback to enhance the user’s haptic experience. We focused on an application related to tumor identification during palpation and evaluated the proposed method in an experimental study where users interacted with a haptic device and graphical interface while exploring a virtual model of soft tissue, which represented stiffness distribution of a silicone phantom tissue with embedded hard inclusions. The performance of hard inclusion detection using force feedback only, pseudo-haptic feedback only, and the combination of the two feedbacks was compared with the direct hand touch. The combination method and direct hand touch had no significant difference in the detection results. Compared with the force feedback alone, our method increased the sensitivity by 5 %, the positive predictive value by 4 %, and decreased detection time by 48.7 %. The proposed methodology has great potential for robot-assisted minimally invasive surgery and in all applications where remote haptic feedback is needed.

Haptics for Multi-fingered Palpation

by Kaspar Althoefer, Shan Luo, Prokar Dasgupta, and Min Li

During open surgery, surgeons can perceive the locations of tumors inside soft-tissue organs usin... more During open surgery, surgeons can perceive the locations of tumors inside soft-tissue organs using their fingers. Palpating an organ, surgeons acquire distributed pressure (tactile) information that can be interpreted as stiffness distribution across the organan important aid in detecting buried tumors in otherwise healthy tissue. Previous research has focused on haptic systems to feedback the tactile sensation experienced during palpation to the surgeon during minimally invasive. However, the control complexity and high cost of tactile actuators limits its current application. This paper describes a pneumatic multi-fingered haptic feedback system for robotassisted minimally invasive surgery. It simulates soft tissue stiffness by changing the pressure of an air balloon and recreates the deformation of fingers as experienced during palpation. The pneumatic haptic feedback actuator is validated by using finite element analysis. The results prove that the interaction stress between the fingertip and the soft tissue as well as the deformation of fingertips during palpation can be recreated by using our pneumatic multi-fingered haptic feedback method.

Multi-Fingered Haptic Palpation using Pneumatic Feedback Actuators

by Kaspar Althoefer, Thrishantha Nanayakkara, Lakmal D. Seneviratne, Min Li, SHAN LUO, and Prokar Dasgupta

This paper proposes a multi-fingered palpation method which employs pneumatic haptic feedback act... more This paper proposes a multi-fingered palpation method which employs pneumatic haptic feedback actuators allowing users to experience haptic sensations at multiple fingers while carrying out remote soft tissue palpation. Pneumatic actuators are used to vary the stress on the user’s fingertips in accordance with the tissue stiffness, experienced during manual palpation. The proposed method reduces actuator elements compared to tactile actuators and provides more information than single-point force feedback. The results of our finite element analysis have proven that our pneumatic haptic feedback device can recreate the contact stress between fingertip and soft tissue during palpation. The accuracy (96.8% vs. 93.3%) and time-efficiency (4.6 s vs. 8.3 s) advantages of using three-fingered over single-fingered palpation have been confirmed in our user study results of stiffness levels discrimination. Relatively good tumor detection sensitivities have been demonstrated by the palpation user study which has showed a direct correlation between tumor size and detection sensitivity and has further proven the efficiency of the proposed actuator and multi-fingered palpation method for tumor detection in palpation simulation.

Pseudo-haptics for rigid tool/soft object interaction feedback in virtual environments

This paper proposes a novel pseudo-haptic soft surface stiffness simulation technique achieved by... more This paper proposes a novel pseudo-haptic soft surface stiffness simulation technique achieved by displaying the deformation of the soft surface and maneuvering an indenter avatar over a virtual soft surface by means of a touch-sensitive tablet. The visual feedback of the surface deformation and the alterations to the indenter avatar behavior produced by the proposed technique create the illusion of interaction with a hard inclusion embedded in the virtual soft surface. The proposed pseudo-haptics technique is validated with a series of experiments conducted by employing a tablet computer with an S-pen input and a tablet computer with a bare finger input. Tablet computers provide unique opportunities for presenting the pseudo-haptic (indenter avatar speed), haptic (contact reaction force from the device surface) and visual cues (surface information) at the same active point of interaction which facilitates information fusion. Hence, here, we evaluate the performance of tablet computers in identification of hard inclusions within virtual soft objects and compare it with the performance of a touchpad input device. A direct hand-soft surface interaction is used for benchmarking of this study. We found that compared with using a touchpad, both the sensitivity and the positive predictive value of the hard inclusion detection can be significantly improved by 33.3% and 13.9%, respectively, by employing tablet computers. Using tablet computers could produce results comparable to the direct hand-soft surface interaction in detecting hard inclusions in a soft object. The experimental results presented here confirm the potential of the proposed technique for conveying haptic information in rigid tool / soft surface interaction in virtual environments.

Multi-fingered haptic palpation utilizing granular jamming stiffness feedback actuators

by Kaspar Althoefer, Helge A Wurdemann, Lakmal D. Seneviratne, Min Li, Sina Sareh, Prokar Dasgupta, and Tommaso Ranzani

This paper describes a multi-fingered haptic palpation method using stiffness feedback actuators ... more This paper describes a multi-fingered haptic palpation method using stiffness feedback actuators for simulating tissue palpation procedures in traditional and robot-assisted minimally invasive surgery. Soft tissue stiffness is simulated by changing the stiffness property of the actuator during palpation. For the first time, granular jamming and pneumatic air actuation are combined together to realize stiffness modulation. The stiffness feedback actuator is validated by stiffness measurements in indentation tests and through stiffness discrimination based on a user study. According to the indentation test results, the introduction of a pneumatic chamber to granular jamming can amplify the stiffness variation range and reduce hysteresis of the actuator. The advantage of multi-fingered palpation using the proposed actuators is proven by the comparison of the results of the stiffness discrimination performance using two-fingered (sensitivity: 82.2%, specificity: 88.9%, positive predicative value: 80.0%, accuracy: 85.4%, time: 4.84 s) and single-fingered (sensitivity: 76.4%, specificity: 85.7%, positive predicative value: 75.3%, accuracy: 81.8%, time: 7.48 s) stiffness feedback.

Multi-Fingered Palpation using Pseudo-Haptic Feedback

Hamlyn Symposium on Medical Robotics, Jul 2014

The inclusion of haptic palpation in training simulators is beneficial for the acquisition of pra... more The inclusion of haptic palpation in training simulators is beneficial for the acquisition of practical experience. Pseudo-haptic feedback, which creates an illusion of force and haptic feedback using only visual information, can replace expensive haptic devices [1]. In this paper, a multi-fingered palpation simulation using pseudo-haptic feedback with three indenter avatars is introduced and evaluated to prove the hypothesis that multi-fingered palpation is more time-efficient than single-fingered palpation. Multi-fingered palpation is more common than single-fingered palpation in real practice when attempting to detect differences in stiffness in the examined tissue [2]. With multiple indenter avatars, a wider tissue area can be investigated during one indentation instead of only one spot using a single indenter avatar. Moreover, the user can conveniently compare the stiffness values at different locations by observing the differences of indentation depths of those separate indenter avatars.

A novel tumor localization method using haptic palpation based on soft tissue probing data

by Kaspar Althoefer, Min Li, Jelizaveta Konstantinova, Lakmal D. Seneviratne, and Prokar Dasgupta

Proceedings of IEEE International Conference on Robotics and Automation (ICRA), 2014

Current surgical tele-manipulators do not provide explicit haptic feedback during soft tissue pal... more Current surgical tele-manipulators do not provide explicit haptic feedback during soft tissue palpation. Haptic information could improve the clinical outcomes significantly and help to detect hard inclusions within soft-tissue organs indicating potential abnormalities. However, system instability is often caught by direct force feedback. In this paper, a new approach to intra-operative tumor localization is introduced. A virtual-environment tissue model is created based on the reconstructed surface of a soft-tissue organ using a Kinect depth sensor and the organ’s stiffness distribution acquired during rolling indentation measurements. Palpation applied to this tissue model is haptically fed back to the user. In contrast to previous work, our method avoids the control issues inherent to systems that provide direct force feedback. We demonstrate the feasibility of this method by evaluating the performance of our tumor localization method on a soft tissue phantom containing buried stiff nodules. Results show that participants can identify the embedded tumors; the proposed method performed nearly as well as manual palpation

Intra-operative tumour localisation in robot-assisted minimally invasive surgery: A review

by Kaspar Althoefer, Lakmal D. Seneviratne, Min Li, Prokar Dasgupta, and Allen Jiang

Robot-assisted minimally invasive surgery has many advantages compared to conventional open surge... more Robot-assisted minimally invasive surgery has many advantages compared to conventional open surgery and also certain drawbacks: it causes less operative trauma and faster recovery times but does not allow for direct tumour palpation as is the case in open surgery. This article reviews state-of-the-art intra-operative tumour localisation methods used in robot-assisted minimally invasive surgery and in particular methods that employ force-based sensing, tactile-based sensing, and medical imaging techniques. The limitations and challenges of these methods are discussed and future research directions are proposed.