Actuation Scheme Research Articles

Hybridized neural network inspired behavioural modelling of pneumatic artificial muscles for assistive robotic applications

PurposeThis paper aims to devise a first-of-its-kind methodology to determine the design, operating conditions and actuation strategy of pneumatic artificial muscles (PAMs) for assistive robotic applications. This requires extensive characterization, data set generation and meaningful modelling between PAM characteristics and design variables. Such a characterization should cover a wide range of design and operation parameters. This is a stepping stone towards generating a design guide for this highly popular compliant actuator, just like any conventional element of a mechanism.Design/methodology/approachCharacterization of a large pool of custom fabricated PAMs of varying designs is performed to determine their static and dynamic behaviours. Metaheuristic optimizer-based artificial neural network (ANN) structures are used to determine eight different models representing PAM behaviour. The assistance of knee flexion during level walking is targeted for evaluating the applicability of the developed actuator by attaching a PAM across the joint. Accordingly, the PAM design and the actuation strategy are optimized through a tabletop emulator.FindingsThe dependence of passive length, static contraction, dynamic step response for inflation and deflation of the PAMs on their design dimensions and operating parameters is successfully modelled by the ANNs. The efficacy of these models is investigated to successfully optimize the PAM design, operation parameters and actuation strategy for using a PAM in assisting knee flexion in human gait.Originality/valueCharacterization of static and the dynamic behaviour of a large pool of PAMs with varying designs over a wide range of operating conditions is the novel feature in this article. A lucid customizable fabrication technique is discussed to obtain a wide variety of PAM designs. Metaheuristic-based ANNs are used for tackling high non-linearity in data while modelling the PAM behaviour. An innovative tabletop emulator is used for investigating the utility of the models in the possible application of PAMs in assistive robotics.

Adaptive Pattern and Motion Control of Magnetic Microrobotic Swarms

Reconfigurable microrobotic swarms and controllable active matter systems have drawn extensive attention recently. Developing effective actuation strategies and control schemes that enable embodied intelligence of microscopic swarms are both major challenges. In this work, we realize the generation of an elliptical paramagnetic nanoparticle swarm (EPNS) with enhanced dexterity for adaptive locomotion, and subsequently a fuzzy control strategy is developed for automatically tuning pattern deformation, orientation, and position of the swarm. By adjusting the input field, the aspect ratio of the EPNS will change accordingly, and we demonstrate its adaptive navigation through curved and narrowed channel by performing pattern reconfigurations. Moreover, using the proposed control strategy, precise matches can be reached between the controlled swarms and the desired patterns. Finally, to show the high compatibility of the control strategy, we employ ribbon-like colloidal swarms driven by oscillating magnetic field, and the results also validate the effectiveness of the strategy.

Technologies for Risk Mitigation and Support of Impaired Drivers

This editorial serves as an extended introduction to the Special Issue on Technologies for Risk Mitigation and Support of Impaired Drivers. It gives the context to recent advances in assisted and automated driving and the new challenges that arise when modern technology meets human users. The Special Issue focuses on the development of robust sensors and detection algorithms for driver state monitoring of fatigue, stress, and inattention, and on the development of personalized multimodal, user-oriented, and adaptive information, warning, actuation, and handover strategies. A summary of more recent developments serves as a motivation for each article that follows.

Current State of Robotics in Hand Rehabilitation after Stroke: A Systematic Review

Among the methods of hand function rehabilitation after stroke, robot-assisted rehabilitation is widely used, and the use of hand rehabilitation robots can provide functional training of the hand or assist the paralyzed hand with activities of daily living. However, patients with hand disorders consistently report that the needs of some users are not being met. The purpose of this review is to understand the reasons why these user needs are not being adequately addressed, to explore research on hand rehabilitation robots, to review their current state of research in recent years, and to summarize future trends in the hope that it will be useful to researchers in this research area. This review summarizes the techniques in this paper in a systematic way. We first provide a comprehensive review of research institutions, commercial products, and literature. Thus, the state of the art and deficiencies of functional hand rehabilitation robots are sought and guide the development of subsequent hand rehabilitation robots. This review focuses specifically on the actuation and control of hand functional rehabilitation robots, as user needs are primarily focused on actuation and control strategies. We also review hand detection technologies and compare them with patient needs. The results show that the trends in recent years are more inclined to pursue new lightweight materials to improve hand adaptability, investigating intelligent control methods for human-robot interaction in hand functional rehabilitation robots to improve control robustness and accuracy, and VR virtual task positioning to improve the effectiveness of active rehabilitation training.

Programmable Morphing Hydrogels for Soft Actuators and Robots: From Structure Designs to Active Functions.

Nature provides abundant inspiration and elegant paradigms for the development of smart materials that can actuate, morph, and move on demand. One remarkable capacity of living organisms is to adapt their shapes or positions in response to stimuli. Programmed deformations or movements in plant organs are mainly driven by water absorption/dehydration of cells, while versatile motions of mollusks are based on contraction/extension of muscles. Understanding the general principles of these morphing and motion behaviors can give rise to disruptive technologies for soft robotics, flexible electronics, biomedical devices, etc. As one kind of intelligent material, hydrogels with high similarity to soft biotissues and diverse responses to external stimuli are an ideal candidate to construct soft actuators and robots.The objective of this Account is to give an overview of the fundamental principles for controllable deformations and motions of hydrogels, with a focus on the structure designs and responsive functions of the corresponding soft actuators and robots. This field has been rapidly developed in recent years with a growing understanding of working principles in natural organisms and a substantial revolution of manufacturing technologies to devise bioinspired hydrogel systems with desired structures. Diverse morphing hydrogels and soft actuators/robots have been developed on the basis of several pioneering works, ranging from bending and folding deformations of bilayer hydrogels to self-shaping of non-Euclidean hydrogel surfaces, and from thermoactuated bilayer gel "hands" to electrodriven polyelectrolyte gel "worms". These morphing hydrogels have demonstrated active functions and versatile applications in biomedical and engineering fields.In this Account, we discuss recent progress in morphing hydrogels and highlight the design principles and relevant applications. First, we introduce the fundamentals of basic deformation modes, together with generic structure features, actuation strategies, and morphing mechanisms. The advantages of in-plane gradient structures are highlighted for programmable deformations by harnessing the out-of-plane buckling with bistability nature to obtain sophisticated three-dimensional configurations. Next, we give an overview of soft actuators and robots based on morphing hydrogels and focus on the working principles of the active systems with different structure designs. We discuss the advancements of hydrogel-based soft robots capable of swift locomotion with different gaits and emphasize the significances of structure control and dynamic actuation. Then we summarize versatile applications of hydrogel-based actuators and robots in biomedicines, cargo delivery, soft electronics, information encryption, and so forth. Some hydrogel robots with a built-in feedback loop and self-sensing system exhibit collaborative functions and advanced intelligence that are informative for the design of next-generation hydrogel machines. Finally, concluding remarks are given to discuss future opportunities and remaining challenges in this field. For example, miniature hydrogel-based actuators/robots with therapeutic or diagnostic functions are highly desired for biomedical applications. The morphing mechanisms summarized in this Account should be applicable to other responsive materials. We hope that this Account will inspire more scientists to be involved in this emerging area and make contributions to reveal novel working principles, design multifunctional soft machines, and explore applications in diverse fields.

Directional droplet transport on switchable ratchets by mechanowetting

Materials with a mechanical response to an external stimulus are promising for application in miniaturized cargo and fluid manipulation in microfluidic (lab-on-a-chip) systems and microsystems in general. One of the main challenges in droplet microfluidics is the precise control of the droplet motion, and existing technologies have drawbacks that can compromise the droplet contents. Here, we demonstrate how an on–off switchable ratchet topography combined with a simple actuation strategy can be exploited to accurately manipulate mm-sized droplets. Because of the mechanowetting principle, the three-phase line dynamically attaches to these deforming ratchets, affecting the droplet displacement in a controlled matter. We show that such topographies are capable of transporting droplets over a surface in a stepwise fashion. We calculate the forces generated by the surface using both a theoretical description of the three-phase line and fluid simulations, and we identify the window of applicability in terms of the droplet size relative to the sawtooth dimensions. Our results enable the design of microfluidic systems with deforming wall topographies for controlled droplet manipulation.

A Novel Semiemperical Friction Coefficient Model Between Needle and Polyvinyl Alcohol Tissue Phantom and Its Validation by Using Computational Inverse Technique

Abstract Needle–tissue interactive force is vital for developing a virtual simulation and planning system (SPS) and optimizing needle control strategy, wherein the friction coefficient is an important parameter but difficult to pre-determine. The existing studies on friction coefficient estimation were lack of qualitative analysis and did not consider the effect of normal pressure and interactive velocity, which may lead to the inaccuracy of the friction calculation. In this paper, we proposed a novel semiempirical friction coefficient model based on the modified classical elastic friction theory that constructs the relationship between the friction coefficient and parameters such as the normal pressure and velocity. The proposed friction coefficient model is validated by using the computational inverse technique based on coupled finite element material point (CFEMP) contact algorithm. The results show that the friction coefficient between the needle and polyvinyl alcohol (PVA) tissue phantom varies from 0.091 to 0.242 with different normal pressure (7.95–17.80 kPa) and insertion velocity (1–9 mm/s), which agrees well with the experimental data. The results of the paper can help to better understand the intrinsic characteristics of the needle–tissue interactions and optimal needle actuation strategies.

Resilient State Estimation and Control of Cyber-Physical Systems Against False Data Injection Attacks on Both Actuator and Sensors

This article studies the secure state estimation and control problem of cyber-physical systems, where there are multiple heterogeneous sensing nodes and one actuator which are both under the threat of intermittent false data injection attacks. A specific filter gain is proposed by solving the equality constrained optimization problem so that the attack on the actuator does not affect the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a posteriori</i> estimation error of the system. A new method to construct <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\chi ^2$</tex-math></inline-formula> detection variables is proposed, which does not require that the covariance matrix be invertible, and then the actuator and sensor attack detection schemes are developed, respectively. Based on the detection results, a multiple information fusion algorithm is developed and an estimator-based controller with the compensator, which can compensate for the actuator attack in the previous step, is further designed. A necessary and sufficient condition for complete compensation is provided, and the stability of the filter and the control system is proved. Finally, the effectiveness of the estimation algorithm and control algorithm is verified by numerical simulation.

SonoTweezer: An Acoustically Powered End-Effector for Underwater Micromanipulation.

Recent advances in contactless micromanipulation strategies have revolutionized prospects of robotic manipulators as next-generation tools for minimally invasive surgeries. In particular, acoustically powered phased arrays offer dexterous means of manipulation both in air and water. Inspired by these phased arrays, we present SonoTweezer: a compact, low-power, and lightweight array of immersible ultrasonic transducers capable of trapping and manipulation of sub-mm sized agents underwater. Based on a parametric investigation with numerical pressure field simulations, we design and create a six-transducer configuration, which is small compared to other reported multi-transducer arrays (16-256 elements). Despite the small size of array, SonoTweezer can reach pressure magnitudes of 300 kPa at a low supply voltage of 25 V to the transducers, which is in the same order of absolute pressure as multi-transducer arrays. Subsequently, we exploit the compactness of our array as an end-effector tool for a robotic manipulator to demonstrate long-range actuation of sub-millimeter agents over a hundred times the agent's body length. Furthermore, a phase-modulation over its individual transducers allows our array to locally maneuver its target agents at sub-mm steps. The ability to manipulate agents underwater makes SonoTweezer suitable for clinical applications considering water's similarity to biological media, e.g., vitreous humor and blood plasma. Finally, we show trapping and manipulation of micro-agents under medical ultrasound (US) imaging modality. This application of our actuation strategy combines the usage of US waves for both imaging and micromanipulation.

Effects of actuation mode on plasma-induced spanwise flow oscillations

Two different plasma actuation strategies for producing near-wall flow oscillations, namely the burst-modulation and beat-frequency mode, are characterized with planar particle image velocimetry in quiescent air. Both concepts are anticipated to work as non-mechanical surrogates of oscillating walls aimed at turbulent flow drag reduction, with the added benefit of no moving parts, as the fluid is purely manipulated by plasma-generated body forces. The current work builds upon established flow-control and proof-of-concept demonstrators, as such, delivering an in-depth characterization of cause and impact of the plasma-induced flow oscillations. Various operational parameter combinations (oscillation frequency, duty cycle and input body force) are investigated. A universal performance diagram that is valid for plasma-based oscillations, independent of the actuation concept is derived. Results show that selected combinations of body force application methods suffice to reproduce oscillating wall dynamics from experimental data. Accordingly, the outcomes of this work can be exploited to create enhanced actuation models for numerical simulations of plasma-induced flow oscillations, by considering the body force as a function of the oscillation phase. Furthermore, as an advantage over physically displaced walls, the exerted body force appears not to be hampered by resonances and therefore remains constant independent of the oscillation frequency. Hence, the effects of individual parameter changes on the plasma actuator performance and fluid response as well as strategies to avoid undesired effects can be determined.

Modeling, Trajectory Analysis and Waypoint Guidance System of a Biomimetic Underwater Vehicle Based on the Flapping Performance of Its Propulsion System

The performance of biomimetic underwater vehicles directly depends on the correct design of their propulsion system and its control. These vehicles can attain highly efficient motion, hovering and thrust by properly moving part(s) of their bodies. In this article, a mathematical modeling and waypoint guidance system for a biomimetic autonomous underwater vehicle (BAUV) is proposed. The BAUV achieves sideways and dorsoventral thunniform motion by flapping its caudal fin through a parallel mechanism. Also, an analysis of the vehicle’s design is presented. A thrust analysis was performed based on the novel propulsion system. Furthermore, the vehicle’s kinematics and dynamic models were derived, where hydrodynamic equations were obtained as well. Computed models were validated using simulations where thrust and moment analysis was employed to visualize the vehicle’s performance while swimming. For the path tracking scheme, a waypoint guidance system was designed to correct the vehicle’s direction toward several positions in space. To accurately obtain waypoints, correction over the propeller’s flapping frequency and bias was employed to achieve proper thrust and orientation of the vehicle. The results from numerical simulations showed how by incorporating this novel propulsion strategy, the BAUV improved its performance when diving and maneuvering based on the dorsoventral and/or sideways configuration of its swimming mode. Furthermore, by designing proper strategies to regulate the flapping performance of its caudal fin, the BAUV followed the desired trajectories. The efficiency for the designed strategy was obtained by comparing the vehicle’s traveled distance and ideal scenarios of straight-line trajectories between targets. During simulations, the designed guidance system presented an efficiency of above 80% for navigation tasks.

Robust active vibration suppression of single-walled carbon nanotube using adaptive sliding-mode control and electrostatic actuators

In this paper, the electrostatic actuator-based active vibration control of a single-wall carbon nanotube conveying fluid is studied. A double electrostatic actuator scheme is developed and its decoupling method also is proposed. Then, a novel adaptive sliding-mode control (SMC) scheme is developed. The newly proposed scheme future improves existing results from two aspects: (1) the newly proposed adaptive SMC can work well under high uncertain case in which all parameters are uncertain and the uncertainties cannot be separated from control force and (2) a double electrostatic actuators scheme which can suppress the vibration of carbon nanotube in multiple directions is designed, and a novel decoupling scheme for the two actuators is developed. The stability of the closed-loop system is analyzed by using Lyapunov stability theory. Finally, the simulation results illustrate the effectiveness of the proposed scheme.

Heat-Mitigated Design and Lorentz Force-Based Steering of an MRI-Driven Microcatheter toward Minimally Invasive Surgery.

Catheters integrated with microcoils for electromagnetic steering under the high, uniform magnetic field within magnetic resonance (MR) scanners (3–7 Tesla) have enabled an alternative approach for active catheter operations. Achieving larger ranges of tip motion for Lorentz force‐based steering have previously been dependent on using high power coupled with active cooling, bulkier catheter designs, or introducing additional microcoil sets along the catheter. This work proposes an alternative approach using a heat‐mitigated design and actuation strategy for a magnetic resonance imaging (MRI)‐driven microcatheter. A quad‐configuration microcoil (QCM) design is introduced, allowing miniaturization of existing MRI‐driven, Lorentz force‐based catheters down to 1‐mm diameters with minimal power consumption (0.44 W). Heating concerns are experimentally validated using noninvasive MRI thermometry. The Cosserat model is implemented within an MR scanner and results demonstrate a desired tip range up to 110° with 4° error. The QCM is used to validate the proposed model and power‐optimized steering algorithm using an MRI‐compatible neurovascular phantom and ex vivo kidney tissue. The power‐optimized tip orientation controller conserves as much as 25% power regardless of the catheter's initial orientation. These results demonstrate the implementation of an MRI‐driven, electromagnetic catheter steering platform for minimally invasive surgical applications without the need for camera feedback or manual advancement via guidewires. The incorporation of such system in clinics using the proposed design and actuation strategy can further improve the safety and reliability of future MRI‐driven active catheter operations.

Motor unit buckling in variable recruitment fluidic artificial muscle bundles: implications and mitigations

Fluidic artificial muscles (FAMs) are a popular actuation choice due to their compliant nature and high force-to-weight ratio. Variable recruitment is a bio-inspired actuation strategy in which multiple FAMs are combined into motor units that can be pressurized sequentially according to load demand. In a traditional ‘fixed-end’ variable recruitment FAM bundle, inactive units and activated units that are past free strain will compress and buckle outward, resulting in resistive forces that reduce overall bundle force output, increase spatial envelope, and reduce operational life. This paper investigates the use of inextensible tendons as a mitigation strategy for preventing resistive forces and outward buckling of inactive and submaximally activated motor units in a variable recruitment FAM bundle. A traditional analytical fixed-end variable recruitment FAM bundle model is modified to account for tendons, and the force–strain spaces of the two configurations are compared while keeping the overall bundle length constant. Actuation efficiency for the two configurations is compared for two different cases: one case in which the radii of all FAMs within the bundle are equivalent, and one case in which the bundles are sized to consume the same amount of working fluid volume at maximum contraction. Efficiency benefits can be found for either configuration for different locations within their shared force–strain space, so depending on the loading requirements, one configuration may be more efficient than the other. Additionally, a study is performed to quantify the increase in spatial envelope caused by the outward buckling of inactive or low-pressure motor units. It was found that at full activation of recruitment states 1, 2, and 3, the tendoned configuration has a significantly higher volumetric energy density than the fixed-end configuration, indicating that the tendoned configuration has more actuation potential for a given spatial envelope. Overall, the results show that using a resistive force mitigation strategy such as tendons can completely eliminate resistive forces, increase volumetric energy density, and increase system efficiency for certain loading cases. Thus, there is a compelling case to be made for the use of tendoned FAMs in variable recruitment bundles.

Computational Analysis of Actuation Techniques Impact on the Flow Control around the Ahmed Body

Active flow control with jet devices is a promising approach for vehicle aerodynamics control. In this work an extended computational study is performed comparing three different actuation strategies for active flow control around the square back Ahmed body at Reynolds number 500,000 (based on the vehicle height). Numerical simulations are run using a Large Eddy Simulation (LES) approach, well adapted to calculate the unsteady high Reynolds number flow control using periodic jet devices. computations are validated comparing to in-house experiments for uncontrolled and some controlled cases. The novelty of this investigation is mainly related to the in-depth study of the base flow and actuation approaches by an accurate LES method and their comparison to experiments. Here, several simulations are performed to estimate the effect of active controls on the flow topology and the drag reduction. Beside the continuous blowing jet, three periodic actuation techniques including periodic blowing and suction as well as the zero flux synthetic jet devices are explored. The slots are implemented discontinuously in order to achieve a better control efficiency linked to vortex generation. In this framework, spectral analyses on global aerodynamical quantities, rear pressure/drag coefficient behavior examination as well as wake structure investigations are performed in order to compare these jet actuations. As a result, shear layer variations are observed during the blowing phase, but the main flow topology change occurs with suction and synthetic jets. Rear back pressure is therefore substantially increased.

Study on snap-through actuation for the bistable composite laminated shell–MFC assembly

All available theoretical researches on the bistable composite laminated shell–MFC assembly have been fundamentally concerned with the static snap-through, while dynamic researches on the assembly have been more pronounced based on experiments for the dynamic snap-through. However, theoretical researches on both the static and dynamic snap-through for the assembly have hardly been carried out. In this article, the theoretical model for the bistable composite laminated shell–MFC assembly is elaborated, elucidating the static and dynamic snap-through by deploying the static and dynamic voltages. To initiate the static snap-through, the voltage–curvature and voltage–displacement curves are graphically presented, delivering the whole path of the process of the static actuation. To initiate the dynamic snap-through, the assembly is activated dynamically while the MFC actuator is expanded by the dynamic voltage. The dynamic responses for the assembly are characterized by the limit-cycle oscillation, the periodic, and chaotic snap-through and the secondary Hopf bifurcation. The theoretical model proofs the bistable composite laminated shell–MFC assembly to be developed and promising, which provides a validation source for the actuation strategy of the desirable snap-through and the suppression strategy of the undesirable snap-through.

Design of a Tensegrity Servo-Actuated Structure for Civil Applications

Abstract The use of glass elements in civil engineering is spreading in the last years beyond merely esthetic functions for their ease of installation and production. Nonetheless, the structural performance of such materials in any condition of use is the object of investigation. In this scenario, the paper analyses the performance of an innovative concept of tensegrity floor (patent no. 0001426973) characterized by a particular steel–glass adhesive junction that permits a profitable structural cooperation between such basically different materials. As known, at the base of the effectiveness of tensegrity structures lies the correct tensioning of metal strands which are devoted at keeping the rigid elements compressed. The tensioning level is then responsible of the actual deformation of the structure, which is of course of uttermost importance while speaking of civil applications. To address this issue with the adequate level of confidence required by construction practice, a mechatronic servo-system is proposed, aimed at maintaining, and modifying when needed, the stress state of the metal cables to adjust the deformation of the upper plane in response to varying loads. Three different actuation schemes, with different levels of realization complexity, are analyzed and compared in simulated environment by means of a hybrid multibody-finite elements model.

Controllable high-performance liquid marble micromixer.

A liquid marble is a liquid droplet coated with a shell of microparticles. Liquid marbles have served as a unique microreactor for chemical reactions and cell culture. Mixing is an essential task for liquid marbles as a microreactor. However, the potential of liquid marble-based microreactors is significantly limited due to the lack of effective mixing strategies. Most mixing strategies used manual and contact-based actuation schemes. This paper reports the development of a manipulation scheme that induces fluid motion into a liquid marble, leading to enhanced mixing. By inducing rotation on a horizontal axis, we significantly increased the mixing rate by 27.6 times compared to a non-actuated liquid marble and reduced the reaction time by more than 10 times. The proposed method provides a simple, continuous, precise, and controllable high-performance mixing strategy on a liquid marble platform.

Modeling for Hybrid Obstacle-Aided Locomotion (HOAL) of Snake Robots

Snake robots able to operate in cluttered environments will be fit for a multitude of applications pertinent for society such as search-and-rescue operations, fire fighting and traversing otherwise unavailable tight spaces. Obstacle-aided locomotion is a propulsion strategy suitable for such applications, where obstacles in the workspace of the robot are used as assets for forward propulsion instead of avoided as hindrances in the path of the snake. To enable this, this paper extends and adapts the notion of classical hybrid position/force control and related concepts to obstacle-aided locomotion of snake robots. The resulting framework is denoted Hybrid Obstacle-Aided Locomotion (HOAL). The resulting library of concepts and notations and a suitable model of the snake robot and its environment enable us to partition the available degrees of freedom into orthogonal subspaces where control schemes for force and motion can be implemented independently. Furthermore, part of the mathematical model that makes up HOAL is presented to motivate its functionality.

Real driving energy consumption and CO2 & pollutant emission characteristics of a parallel plug-in hybrid electric vehicle under different propulsion modes

PHEVs (Plug-in hybrid electric vehicles) are thought to be energy and environment friendly, while these conclusions are seldom verified during real driving tests. To evaluate PHEV real driving energy consumption, CO2 emission, and pollutants emission, one parallel PHEV was tested under real driving condition. The results indicate that the distance-specific energy consumption of CD (charge depleting) mode, compared with the CS (charge sustaining) mode, is 45% lower for WTW (Well to Wheel) evaluation. The CD WTW CO2 emission is 50% higher than the CS due to the electricity generation CO2 intensity. CD and CS mode could have similar CO2 emission when electricity CO2 intensity reaches 397.50 g/kWh. The limited charging reduced the PHEV energy conservation by around 50%, but the WTW CO2 emission is also reduced. Contrary to common belief, the PHEV CD mode real driving emission is underestimated, and it could be over 30 times higher than the CS mode. The deteriorated CD emission is caused by the inaccurate power demand prejudgments and frequent engine cold high-power re-start. The driving pattern comparison reveals that the deteriorated CD emission should not be a local but global concern. These results could be used for PHEV propulsion strategy optimization and test cycle design.