# modified two point gait

Therefore, a walking robot was built to simulate a paraplegic patient wearing an exoskeleton to conduct a preliminary study for safety reasons. Modified two-point. The unaffected leg is advanced between the crutches to the stairs in a modified three-point gait. We performed a robot walking experiment during the simulation to verify the feasibility of the proposed method. (1987), Hamill et al. Gait patterns .. assistive devices : GAIT- PART II: Gait patterns with assistive devices Canes, crutches and walkers are commonly used assistive devices (AD) … When a human walks, the knee joint of stance leg is fully stretched. (widening the BOS & shifting COG away from protected LE) aid and pt. (9), we can get: By substituting $$z_{M}$$ and $$\ddot{z}_{M}$$ into the Eq. Advanced robotics 24(11):1615–1638, Tsukahara A, Hasegawa Y, Sankai Y (2011) Gait support for complete spinal cord injury patient by synchronized leg-swing with hal. The lower image in Fig. In the real case, the IMU sensor can be attached to the cane to measure its inclination. The ZMP is widely used for gait generation in a humanoid robot. Objective Task-specific training is often used in functional rehabilitation for its potential to improve performance at locomotor tasks in neurological populations. In order to improve the walking stability, the hip joint angle on stance leg during walking was modified based on ZMP. https://doi.org/10.1016/j.jbiomech.2015.07.023. Am J Phys Med Rehabil 91(11):911–921, Kilicarslan A, Prasad S, Grossman RG, Contreras-Vidal JL (2013) High accuracy decoding of user intentions using eeg to control a lower-body exoskeleton. Although the start and stop of walking is controlled by the user incline the body, the user still needs to adjust the angle and fall point of the canes to cooperate with the gait of the exoskeleton. where $$\Gamma$$ is the matrix of the eigenvectors in descending order concerning the eigenvalues. A swing-through gait 4. • Followed by the non-affected leg. In the case of robot walking without gait modification, the motion of the cane was extracted from a subject walking with a cane, and the gait was generated by human walking synergy using the cane motion as input. The weight of the walking robot is 25 [kg] with 16 degrees of freedom. Comparison of human gait, gait generated suing synergy and modified gait. The x-axis is the angle change of the cane in 0.08 [s] after it starts to swing whereas the y-axis refers to the walking cycle and step length, respectively. Assume the $$Z_{M}$$ is constant, this model becomes a linear inverted pendulum (LIP), and the solution can be written as: where $$z_{M}$$ is a constant. The inverted pendulum model has a constant length r, the CoM is assumed concentrated at the tip of the pendulum, and the angle between the pendulum and the vertical direction is $$\theta$$. Sequence : … There are three basic positions that a rider can use: two-point position, in which the rider’s two legs are against the horse, while the seat is out of the saddle; three-point position, in which the rider’s two legs and seat are in contact with the horse; and modified three-point position, in which the rider’s two legs and only his crotch are in contact with the horse. LE and aid advance alternately (four-point) or simultaneously (two-point) ; aid is typically used on the contralateral side Department of Micro-Nano Mechanical Science and Engineering, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan, Mengze Li, Tadayoshi Aoyama & Yasuhisa Hasegawa, You can also search for this author in Hassan proposed an instrumented cane to help hemiplegic patients walk with the help of an exoskeleton [22,23,24]. The system allows the patient to hold a pair of canes in order to keep balance, and does not contribute to keeping balance without the patient’s action. Place the patient in the tripod position and instruct him to do the following. Quasi-passive leg utilizes only spring and damper to augment load-carrying during walking [2]. (12), we can get the trajectory of ZMP. Huang in proposed a stable gait generator based on a newly proposed gait pattern in using the interpolation function. 7 is the side view of the robot walking. We use cookies to help provide and enhance our service and tailor content and ads. Besides, Principal component analysis (PCA) is often used to analyze human synergy to extract the coupling relationship between limbs. This synergy synchronizes the walking motion and the intention of user. The use of human walking synergy to generate gait can solve the problems of synchronization between user intention and exoskeleton motion as well as human-like gait. The upper image in Fig. The shoulder has one degree of freedom, and the crutches can be stretched and shortened meanwhile the robot can adjust its center of gravity to maintain balance. "Motion planning using NIP and ZMP" section introduces ZMP and NIP for motion planning. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. Crocher et al. Matthew et al. In the three-point gait with mono and quadripod canes, subjects were asked to first move the WSFC forward, then the paretic-side foot, and finally the nonparetic-side foot. In the present study we use a nonlinear inverted pendulum (NIP) to generate the CoM trajectory, subsequently, the leg joint angle can be obtained by solving the inverse kinematics. The use of NIP ensures that the modified walking trajectory is similar to the human walking trajectory. Li, M., Aoyama, T. & Hasegawa, Y. Gait modification for improving walking stability of exoskeleton assisted paraplegic patient. The minor contribution of this paper is on the utilization of canes as an interface to synchronize the user’s intention and leg motion. ROBOMECH Journal The affected leg is advanced between the crutches to the stairs in a modified two-point gait. IEEE Transact Neural Syst Rehabil Eng 17(1):23–30, Vallery H, Buss M (2006) Complementary limb motion estimation based on interjoint coordination using principal components analysis. As shown in figure 4, assuming the hip joint angle on stance leg when a step is taken is $$\theta _{0}^{*}$$, the inclination angle of the pendulum when it starts to move is $$\theta _{0}$$, the modified hip joint angle trajectory of stance $$\theta ^{*}$$ can be obtained by: where $$\theta ^{*}$$ is used to replace the hip joint angle of support leg, $$\theta _{sp}^{h}$$, which is mentioned in "Gait generation based on walking NeuroRex uses non-invasive electroencephalography to decode a paraplegic patient motion intent and aid walking [5]. Instruct the patient to move the cane and the weak or affected foot forward in unison (i.e at the same time), keeping the cane close to the body to prevent leaning to the side. Figure 8 shows the ZMP measurement results of the walking experiment. The walking was divided into the walking phase and stance phase. Re-walk enables spinal cord injured patients to walk without human assistance [4]. The transfer of the CoM happens at the walking phase and the stance legs aid the CoM to move forward. Given the walking cycle and step length, the hip joint trajectory of the stance leg can be generated using NIP. (10), we can get: where the $$a_{1}$$, $$a_{2}$$, $$a_{3}$$ and $$a_{4}$$ are: Therefore, the parameters to determine the solution function of Eq. A swing-through gait. When the ratio is less than 0.5, there is almost no difference between ZMP and reference ZMP. To mimic the walking conditions of the paraplegic patient, the subjects were asked to support the body with crutches as much as possible during the walk while moving the cane with the leg on the opposite side simultaneously during walking. Instead of a real patient wearing an exoskeleton, a cane robot was used for the Gazebo simulation. For example: Roboknee determines user intent through the knee joint angle and ground reaction forces and allows the wearer to climb stairs [3]. Mengze Li. \end{aligned}$$,$$\begin{aligned} x_{2}=\Gamma _{2} \Gamma _{1}^{\sharp } x_{1}. The pre-programmed trajectory method is not the only solution to generate the exoskeleton movement. Besides, Ekso Bionics developed by Ekso measures the position of the user’s center of gravity and estimates the walking intention of paraplegic patients by detecting the center of mass (CoM) transfer when their upper body is leaned forward [11]. Synonyms for two-point gait in Free Thesaurus. Liu developed a rehabilitation exoskeleton based on the postural synergy that allows the 10 degrees of freedom robot driven by only two actuators [21]. [7] developed a well-known exoskeleton, hybrid assistive limb (HAL), to help physically challenged people to walk again. The rapid development of the exoskeleton has made great achievements in two aspects: (1) augmentation in human strength and durability. 32 33. \end{aligned}$$,$$\begin{aligned} \begin{aligned} x_{1}&=[\theta _{l} \quad \theta _{r}]^{T}, \\ x_{2}&=[\theta _{sw}^{h} \quad \theta _{sw}^{k} \quad \theta _{sp}^{h} \quad \theta _{sp}^{k}]^{T}. Since walking is a highly coupled cooperative motion between upper and lower limbs, the walking cycle and step length can be related to the motion of cane. p 363–372, Hassan M, Kadone H, Suzuki K, Sankai Y (2012) Exoskeleton robot control based on cane and body joint synergies. \end{aligned}$$,$$\begin{aligned} x_{ZMP} = x_{M} - \frac{\ddot{x}_{M} z_{M}}{\ddot{z}_{M}+g}. The walking synergy was extracted from a healthy subject and applied to synchronize the exoskeleton’s movement with the user’s intention. Since the $$\Gamma$$ is an orthonormal matrix, then x could be rewritten as: then $$\Gamma$$ could be separated for the known variables $$x_{1}$$ and the unknown variables $$x_{2}$$: where $$\Gamma _{1}$$ and $$\Gamma _{2}$$ are the separated matrix for the known and unknown variables, respectively. This pattern is less stable than the four-point pattern. In: The 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, IEEE. The details can be described below. A modified vector coding (VC) technique was used to quantify lumbar–pelvic coordination during gait. In this case, it is necessary to judge whether the error has a significant effect on the stability of walking (i.e. Furthermore, a nonlinear inverted pendulum (NIP) model was utilized in order to generate a gait with a fully stretched knee joint angle that is similar to human gait. Figure 5 shows the relationship between the walking cycle and angular change of cane in 0.08 [s] as well as between step length and angular change of cane in 0.08 [s]. Linear inverted pendulum (LIP) model is widely used in the trajectory planning [29, 30]. This paper is organized as follows: "Gait generation based on walking synergy" section introduces PCA to extract the walking synergy between cane and leg motion from data of subject walking with canes. The proposed method was verified via the Gazebo simulation using a walking robot to simulate a patient wearing an exoskeleton. studied the synergy between arms and legs by measuring the electromyographic on leg and arms during walking [15]. - on unaffected side ... - Utilizes TWO crutches or walker - TWO canes only used when pt w/o WB restrictions - Restricted WB on one LE, FWB on other. The small discrepancy shows that the generated joint angle has high similarity with the joint of human walking. This pattern is less stable than the four-point pattern. synergy", http://creativecommons.org/licenses/by/4.0/, https://doi.org/10.1186/s40648-020-00169-y. J Neurophysiol 97(2):1809–1818, Dietz V, Fouad K, Bastiaanse C (2001) Neuronal coordination of arm and leg movements during human locomotion. volume 7, Article number: 21 (2020) 3.Modified four-point and two-point Gait patterns: In the case of walking without gait modification, the maximum error between ZMP and reference ZMP was 0.434 [m] with an average error of 0.050 [m]. Instead of applying the arm joint trajectories, the cane inclination were used as the known variable matrix $$x_{1}$$. This is mainly due to the robot change from stationary to motion, and the maintenance of balance is changed from 4-point to 2-point support. In [8], HAL detects a preliminary motion to enhance the transfer between standing and sitting for complete paraplegic patients. For the NIP, the length of the pendulum remains constant and the generated walking motion has a fully stretched knee joint on stance leg, which is similar to the human walking habit. We compared the robot walking with and without gait modification. It is noteworthy to mention that using the cane as the interface does not increase the burden of the patients as the purpose is only to keep balance. The major contribution in this paper is the gait modification method based on ZMP to improve the walking stability of a paraplegic patient wearing an exoskeleton. It was found that this difference is mainly related to the ratio between the step length and pendulum length. The researches about human walking synergy make non-pre-programmed trajectory generation possible. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. (2000) described the ‘coupling angle’ (CA) which refers to the vector orientation between two adjacent time points on an angle–angle diagram relative to the right horizontal (Fig. 2: p 4637–4640, Crocher V, Sahbani A, Robertson J, Roby-Brami A, Morel G (2012) Constraining upper limb synergies of hemiparetic patients using a robotic exoskeleton in the perspective of neuro-rehabilitation. Gait analysis is the systematic study of animal locomotion, more specifically the study of human motion, using the eye and the brain of observers, augmented by instrumentation for measuring body movements, body mechanics, and the activity of the muscles. (1) Move the right leg and left crutch forward together. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. Using a modified technique presented by Sparrow et al. (9) is difficult to find an analytical solution. The two-point gait pattern closely approximates a normal gait pattern and should be encouraged. Proceedings of IEEE International Conference on Robotics and Automation 2:1404–1409. © 2021 BioMed Central Ltd unless otherwise stated. IEEE Transact Neural Syst Rehabil Eng 15(3):379–386, Tsukahara A, Kawanishi R, Hasegawa Y, Sankai Y (2010) Sit-to-stand and stand-to-sit transfer support for complete paraplegic patients with robot suit hal. Three subjects participated in this experiment and comprise of all-male, healthy, aged from 25 to 30 and without any history of movement disorder. We researched the synergy between canes (arms) and legs and confirmed that by using the motion of canes will aid to generate the motion of legs for walking. Antonyms for two-point gait. \end{aligned}$$,$$\begin{aligned} x=\Gamma y. \\ \end{aligned} \end{aligned}$$,$$\begin{aligned} \begin{aligned} C_{1}&= \frac{a_{2} l/2 + a_{4} l/2}{ a_{1} a_{4} - a_{2} a_{3}}, \\ C_{2}&= \frac{a_{1} l/2 + a_{3} l/2}{ a_{1} a_{4} - a_{2} a_{3}}. Firstly, the walking trajectory generated using ZMP becomes stable. Mod 3pt gait pattern with a walker = stable modified two point =Walker and bad leg together = efficient CRUTCHES: three point gait pattern • swing to= more stable • swing through= more efficient reciprocal gait pattern • four point more stable • two point … Errors mostly occur when the robot takes a step and the ZMP gradually converges to the reference ZMP. Contra-lateral Two-point Gait with One Stick Contra lateral hand and … 1. Secondly, the leg motion generated by human walking synergy is similar to the human walking motion. In: 2011 IEEE International Conference on Robotics and Automation, IEEE. The upper image in Fig. Springer Nature. First, a pair of cane is used as an interface to control the user’s walking and then, the synergy between legs and canes is used to synchronize the user’s walking intention during the exoskeleton movement. The blue line represents the joint trajectory extracted from human walking with a cane. Errors mostly occur when the robot takes a step with no convergence of ZMP to the reference ZMP, leading the robot to fall within six steps. Modified four-point. In this way, the walking synergy was used as a gait generator, with the cane inclination angle as input, and the generator generates a joint angle of hip and knee. Numerous interesting researches have focused on improving the performance of humanoid robot walking gesture. The NIP model can be used to generate a stable CoM trajectory, in which the resultant ZMP stays in the support polygon formed by the cane and foot. As push-off impairment are often seen with these patients, this functional approach shows potential to retrain gait overground to normalize the gait pattern and retrain the ability to improve gait speed. Figure 7 shows the simulation scene of robot walking with gait modification. The utilized gait is the fastest and the most efficient, therefore it becomes the target motion in this research and is used to extract the walking synergy. Sensors 14(1):1705–1722, Hassan M, Kadone H, Ueno T, Suzuki K, Sankai Y (2015) Feasibility study of wearable robot control based on upper and lower limbs synergies. The walking gait generated from the walking synergy might not result in a fully stable walk due to the dynamic difference between the lower-limb exoskeleton and a human subject. This Figure includes the data of 50 steps of three subjects walking with a cane. Many orthopedic conditions result in impaired gait. The robot height is 180 [cm] while the width is 70 [cm]. For rapid generation and easy calculation, a combination of a linear inverted pendulum (LIP) and ZMP is often used to generate the walking trajectory in robot gait planning. Daffertshofer et al. Cookies policy. \end{aligned}$$,$$\begin{aligned} \tau = m ( g + \ddot{z}_{M}) ( x_{M} - x_{ZMP}) + m \ddot{x}_{M} z_{M}. The exoskeleton acts directly on the patient’s body, supporting the user’s weight and augment the strength as well as provides a high capability for the paraplegic patient to walk again. Theoretically, The ZMP stays inside the support polygon thereby enabling the exoskeleton to keep stable during walking. \end{aligned}$$,$$\begin{aligned} S_{K}^{\prime }=S_{K}+E_{K-1}, \end{aligned}, "Gait generation based on walking synergy", "Gait generation based on walking Modified two point pattern require only one amb aid, with pattern of simultaneous, reciprocal forward placement of amb and affected LE together followed by the full weight bearing foot. In the simulation, the balance in the lateral plane was kept by the cane. The equation to predict the walking cycle and step length are obtained from this Figure and can be written as: where T is the walking cycle and S is the step length, and $$A_{cane}$$ is the angle change of the cane in 0.08[s] after it started to swing. In addition, the ability to control the robot through human motion synergy still needs to be investigated with real exoskeleton and patient. In the case of this paper, the extracted synergy is contained in a 6 by 6 matrix, and each column corresponds to a principal component (PC). A modified two-point gait. 8 is the ZMP of robot walking without gait modification. The walking motion generated in this way is natural and compatible. In a real case scenario, the exoskeleton is an under-actuated system, it has degrees of freedom in the sagittal and lateral plane, but it only provides support in the sagittal plane. Figure 6 shows the schematic illustrations of the walking robot. the aid is held in UE opposite to LE that requires protection. Among the above-mentioned exoskeletons, exoskeletons for assisting the paraplegic patient have been widely used in scientific research, rehabilitation, and daily life. In: Proceeding of IEEE Conference on computer aided control system design, Proceeding of IEEE International Conference on Control Applications, Proceeding of IEEE International Symposium on Intelligent Control, p 933–938, Sardain P, Bessonnet G (2004) Forces acting on a biped robot center of pressure-zero moment point. \\ \end{aligned} \end{aligned}, \begin{aligned} \theta ^{*}=\theta -(\theta _{0}-\theta _{0}^{*}). The zero moment point (ZMP) was used to modify the walking motion to enhance the walking stability. This is a transitional phase, in which the robot remains still and does not transfer its CoM. The detail explanation of using principal component analysis (PCA) to analyze human walking synergy is described in [25, 26]. PubMed Google Scholar. ... pate in the gait analysis, however two children failed to report for the trial, ... scale subjects can score from 1 to 3 points, except for Item One (1–5 points) and Item Eleven (1–4 points). The LIP assumes a constant height for the center of mass (CoM) which results in a bent knee joint on the stance leg during gait. Clin Biomech 19(4):415–428, Todorov E, Ghahramani Z (2004) Analysis of the synergies underlying complex hand manipulation. The use of NIP makes up for this shortcoming, thereby enables the modified trajectory to conform to human walking habits. 9 synonyms for gait: walk, step, bearing, pace, stride, carriage, tread, manner of walking, pace. In: Proceeding of International Symposium on Micro-NanoMechatronics and Human Science, p 1–6, Vallery H, Van Asseldonk EH, Buss M, Van Der Kooij H (2008) Reference trajectory generation for rehabilitation robots: complementary limb motion estimation. Assuming the step length of walking is l, and the CoM of the pendulum moves from $$-l/2$$ to l/2, the moment of the human to start a step and the pendulum to move is at time $$t_{s}$$, and the moment of the human to end the step and when the pendulum stops moving is at time $$t_{e}$$. If the error is small, the stability of walking becomes unaffected. waddling gait exaggerated alternation of lateral trunk movements with an exaggerated elevation of the hip, suggesting the gait of a duck; characteristic of muscular dystrophy . Each joint of the robot is equipped with an encoder that measures the joint angle during the experiments. The experiment results show that the walking stability was highly improved after gait modification. Scores are based on a 4-point scale: 3) No gait dysfunction 2) Minimal impairment 1) Moderate impairment 0) Severe impairment; Highest possible score is 24 points, and tasks include: 1) Steady state walking 2) Walking with changing speeds 3) Walking with head turns both horizontally and vertically 4) Walking while stepping over and around obstacles The movable joints are the shoulder joints, hip joints, knee joints, and ankle joints.