Mitja Trkov

Rider/bicycle pose estimation with IMU/seat force measurements

Unstable bicycle provides an excellent platform to understand human sensorimotor mechanism for balancing control. We present an instrumented bicycle system to study the dynamic interactions between the human rider and the bicycle. A dynamics model is presented to capture the energetic interactions between the rider and the bicycle. We use and integrate the measurements from the seat force sensor and the rider body-mounted inertial measurement unit (IMU) to estimate both the riders and bicycles poses. Experimental results are presented to demonstrate the capability of the pose estimation development.

A robotic bipedal model for human walking with slips

Slip is the major cause of falls in human locomotion. We present a new bipedal modeling approach to capture and predict human walking locomotion with slips. Compared with the existing bipedal models, the proposed slip walking model includes the human foot rolling effects, the existence of the double-stance gait and active ankle joints. One of the major developments is the relaxation of the nonslip assumption that is used in the existing bipedal models. We conduct extensive experiments to optimize the gait profile parameters and to validate the proposed walking model with slips. The experimental results demonstrate that the model successfully predicts the human recovery gaits with slips.

Shoe-Floor Interactions During Human Slip and Fall: Modeling and Experiments

Shoe-floor interactions such as friction force and deformation/local slip distributions are among the critical factors to determine the risk for potential slip and fall. In this paper, we present modeling, analysis, and experiments to understand the slip and force distributions between the shoe sole and floor surface during the normal gait and the slip and fall gait. The computational results for the slip and friction force distribution are based on the spring-beam networks model. The experiments are conducted with several new sensing techniques. The in-situ contour footprint is accurately measured by a set of laser line generators and image processing algorithms. The force distributions are obtained by combining two types of force sensor measurements: implanted conductive rubber-based force sensor arrays in the shoe sole and six degree-of-freedom (6-DOF) insole force/torque sensors. We demonstrate the sensing system development through extensive experiments. Finally, the new sensing system and modeling framework confirm that the use of required coefficient of friction and the deformation measurements can real-time predict the slip occurrence.Copyright

Study of concrete drilling for automated non-destructive evaluation and rehabilitation system for bridge decks

Robotic drilling is the basic process for the non-destructive rehabilitation (NDR) system in the Automated Non-destructive Evaluation and Rehabilitation System (ANDERS) for bridge decks. In this paper, we present a study and testing of a concrete drilling process that is used for robotic drilling process for bridge decks repair. We first review the ANDERS and NDR design. Then we present the experimental setup for the drilling process study. A set of testing experiments are performed considering drilling process parameters such as drill bit size, drill rotating speed, drill thrust force and types of concrete composites. Based on the experiments and analysis, we identify and find that the optimal set of drilling process parameters for the ANDERS application is 1/4-inch bit size, drill rotational speed of 1500 rpm and thrust force around 35 lbs. We also demonstrate that the monitoring of drill feeding displacement and thrust force cannot be used to detect and identify the cracks in bridge decks.

Balance recovery control of human walking with foot slip

We present a balance recovery control design for human walking with foot slip. The control strategy is built on the two-mass linear inverted pendulum model (LIP) that represents the human body and limb motions. We first validate the model through experiments of human normal walking and walking with foot slip. We then design a balance recovery control using the capture point (CP) concept. We extend the CP-based walking control and incorporate time-varying locations of the zero moment point. These extensions allow the balance recovery control of the humans center of the mass movement to rapidly respond to the unexpected foot slip. We conduct experiments to tune the model parameters and to validate the slip recovery control.

Slip detection and prediction in human walking using only wearable inertial measurement units (IMUs)

Slip and fall is one of the major causes for human injuries for elders and professional workers. Real-time detection and prediction of the foot slip is critical for developing effective assistive and rehabilitation devices to prevent falls and train balance disorder patients. This paper presents a novel real-time slip detection and prediction scheme with wearable inertial measurement units (IMUs). The slip-detection algorithm is built on a new dynamic model for bipedal walking with slips. An extended Kalman filter is designed to reliably predict the foot slip displacement using the wearable IMU measurements and kinematic constraints. The proposed slip detection and prediction scheme has been demonstrated by extensive experiments.

Modeling of pure percussive drilling for autonomous robotic bridge decks rehabilitation

This paper presents a dynamic model of pure percussive drilling for autonomous robotic rehabilitation for concrete bridge decks. We first describe the autonomous mobile manipulator-based concrete drilling system for bridge deck rehabilitation. A dry friction-based pure percussive drilling model is then presented to describe the drilling process characteristics and to capture the influence of drilling conditions and parameters on the penetration rate. One attractive property of the proposed model is the physical interpretation of the crushing/chipping effects in percussive drilling process. The model and its properties are validated and demonstrated through extensive drilling experiments.

Hybrid zero dynamics of human biped walking with foot slip

Most existing bipedal dynamics models are built on an assumption of no foot slip. We relax such assumption and present hybrid zero dynamics model and properties for bipedal walking with foot slip. When foot slips, the biped hybrid zero dynamics (HZD) preserve rich features such as high dimensionality and transitions between slip and non-slip dynamics. We present the closed-form of the HZD for human walking and discuss the transition between non-slip and slip states through slip recovery design. We illustrate the analysis and design through human walking experiments. The proposed HZD models and analysis can be further used to design control systems for robotic rehabilitation and assistive devices.

Shoe–Floor Interactions in Human Walking With Slips: Modeling and Experiments

Shoe-floor interactions play a crucial role in determining the possibility of potential slip and fall during human walking. Biomechanical and tribological parameters influence the friction characteristics between the shoe sole and the floor and the existing work mainly focus on experimental studies. In this paper, we present modeling, analysis, and experiments to understand slip and force distributions between the shoe sole and floor surface during human walking. We present results for both soft and hard sole material. The computational approaches for slip and friction force distributions are presented using a spring-beam networks model. The model predictions match the experimentally observed sole deformations with large soft sole deformation at the beginning and the end stages of the stance, which indicates the increased risk for slip. The experiments confirm that both the previously reported required coefficient of friction (RCOF) and the deformation measurements in this study can be used to predict slip occurrence. Moreover, the deformation and force distribution results reported in this study provide further understanding and knowledge of slip initiation and termination under various biomechanical conditions.

Disturbance observer-based balance control of robotic biped walkers under slip

We present balance recovery control of bipedal robotic walkers under foot slip disturbance. A dynamic model is first presented to capture the bipedal locomotion under slip disturbance. Two different control approaches are presented: one is based on the feedback linearization and the second one uses the disturbance observer (DOB) method. The recovery strategies and profiles are designed through linear inverted models and inspired by human walking locomotion profiles. We present and compare the simulation results under both the feedback linearization- and DOB-based control designs.