While NAND flash memory has continuously increased its storage density over decades, this progress has exacerbated the read-disturbance problem. In this work, we identify two fundamental limitations of existing read-disturbance management techniques that trigger read reclaim (RR) at the block granularity: (i) they overlook the heterogeneous reliability impact of read disturbance across individual wordlines (WLs), leading to unnecessary RR in many cases; and (ii) they address read disturbance only after disturbance-induced errors have already accumulated, which forces substantial RR-induced copy overheads in read-disturbance-prone modern NAND flash memory. To address these limitations, we propose STRAW (STRess-Aware Wordline-based read-disturbance management), a new technique that minimizes RR overheads through two key ideas: (i) stress-aware WL-based read reclaim, which monitors the accumulated read-disturbance effect on each WL and reclaims only heavily disturbed WLs, and (ii) stress-reduced read, which mitigates disturbance on valid WLs during each read operation by scaling pass-through voltages based on WL validity. Our experimental results using a modern SSD emulator show that STRAW reduces RR-induced page-copy overhead by 88.6% on average compared with the state-of-the-art technique.

Although NAND flash memory has achieved continuous capacity improvements via advanced 3D stacking and multi-level cell technologies, these innovations introduce new reliability challenges, particularly lateral charge spreading (LCS), absent in low-capacity 2D flash memory. Since LCS significantly increases retention errors over time, addressing this problem is essential to ensure the lifetime of modern SSDs employing high-capacity 3D flash memory. In this paper, we propose a novel data randomizer, STate-Aware Randomizer (STAR), which proactively eliminates the majority of weak data patterns responsible for retention errors caused by LCS. Unlike existing techniques that target only specific worst-case patterns, STAR effectively removes a broad spectrum of weak patterns, significantly enhancing reliability against LCS. By employing several optimization schemes, STAR can be efficiently integrated into the existing I/O datapath of an SSD controller with negligible timing overhead. To evaluate the proposed STAR scheme, we developed a STAR-aware SSD emulator based on characterization results from 160 real 3D NAND flash chips. Experimental results demonstrate that STAR improves SSD lifetime by up to 2.3× and reduces read latency by an average of 50% on real-world traces compared to conventional SSDs.

While large language models (LLMs) achieve remarkable performance across diverse application domains, their substantial memory demands present challenges, especially on personal devices with limited DRAM capacity.Recent LLM inference engines have introduced SSD offloading for model parameters to reduce memory footprint.However, the highly memory-bound nature of on-device LLMs makes inference speed heavily dependent on read bandwidth, leading to significant performance degradation due to the limited bandwidth of SSDs.In this paper, we propose an in-flash processing solution for on-device LLM, called Accelerator-in-Flash (AiF), which integrates matrix-vector multiplication (GEMV) operations directly into flash chips.By enabling in-flash GEMV operations, AiF leverages the high internal bandwidth of flash chips without being constrained by the limited external bandwidth.Building on this core structure, AiF employs two novel flash read techniques that were specifically optimized for reading LLM parameters stored in flash memory.AiF achieves a 4x boost in internal read bandwidth during inference with minimal implementation overhead, thanks to its streamlined error correction process.Evaluations on eight real-world LLMs reveal that AiF provides a 14.6x throughput improvement compared to baseline SSD offloading schemes.Furthermore, AiF surpasses in-memory inference, delivering 1.4x higher throughput with a significantly reduced memory footprint.

This work investigates a new erase scheme in NAND flash memory to improve the lifetime and performance of modern solid-state drives (SSDs). In NAND flash memory, an erase operation applies a high voltage (e.g., > 20 V) to flash cells for a long time (e.g., > 3.5 ms), which degrades cell endurance and potentially delays user I/O requests. While a large body of prior work has proposed various techniques to mitigate the negative impact of erase operations, no work has yet investigated how erase latency should be set to fully exploit the potential of NAND flash memory; most existing techniques use a fixed latency for every erase operation which is set to cover the worst-case operating conditions. To address this, we propose Aero (Adaptive ERase Operation), a new erase scheme that dynamically adjusts erase latency to be just long enough for reliably erasing target cells, depending on the cells' current erase characteristics. Aero accurately predicts such near-optimal erase latency based on the number of fail bits during an erase operation. To maximize its benefits, we further optimize Aero in two aspects. First, at the beginning of an erase operation, Aero attempts to erase the cells for a short time (e.g., 1 ms), which enables Aero to always obtain the number of fail bits necessary to accurately predict the near-optimal erase latency. Second, Aero aggressively yet safely reduces erase latency by leveraging a large reliability margin present in modern SSDs. We demonstrate the feasibility and reliability of Aero using 160 real 3D NAND flash chips, showing that it enhances SSD lifetime over the conventional erase scheme by 43% without change to existing NAND flash chips. Our system-level evaluation using eleven real-world workloads shows that an AERO-enabled SSD reduces read tail latency by 34% on average over a state-of-the-art technique.

Modern high-performance SSDs have multiple flash channels operating in parallel to achieve their high I/O bandwidth. However, when the effective bandwidth of these flash channels declines, the SSD's overall bandwidth is substantially impacted. In contemporary SSDs featuring high-density 3D NAND flash memory, frequent invocations of a read-retry procedure pose a significant challenge to fully utilizing the maximum I/O bandwidth of a flash channel. In this paper, we propose a novel read-retry optimization scheme, Retry-in-Flash (RiF), which proactively minimizes the amount of time wasted in conventional read-retry procedures. Unlike existing read-retry solutions that focus on identifying an optimal read-reference voltage for a sensed page, the RiF scheme focuses on determining early on whether a read-retry will be required for the sensed data. To know if a read-retry is needed or not at the earliest possible time, we propose a RiF-enabled flash chip with an on-die early-retry (ODEAR) engine. When the ODEAR engine determines that a sensed page requires a read-retry, a readreference voltage is immediately adjusted and the same page is re-read while ignoring the previously sensed page. By performing the key steps of a read-retry procedure inside a RiF flash chip without transferring the sensed uncorrectable page to an offchip controller, the RiF scheme prevents the read bandwidth of a flash channel from being wasted due to failed read data. To evaluate the RiF scheme, we developed a prototype RiF-enabled flash chip and constructed a RiF-aware SSD simulator using RiF flash chips. Our evaluation results show that the proposed RiF scheme improves the effective SSD bandwidth by 72.1% on average over a state-of-the-art read-retry solution at 2K P/E cycles with negligible power and area overheads.

In order to meet the diverse requirements of modern storage systems, flash memory should be optimized by precisely tuning a huge number of internal operating parameters. Although 3D NAND flash memory successfully increases the capacity of storage systems, its complex architecture and unique error behavior make such optimization a more difficult and time-consuming process during NAND manufacturing. This work introduces Norns, a novel method for post-fabrication optimization of NAND flash memory, which is an essential step in the manufacturing process of modern 3D NAND flash memory to simultaneously meet various requirements on reliability, performance, yield, etc. Norns is based on simple machine-learning approaches yet with three key guidelines that leverage (i) domain-specific rules, (ii) recent optimization results, and (iii) online simulation, respectively, to enable quick optimization of a large number of device parameters within the limited product turnaround time (TAT). We evaluate Norns in mass production for 7th-generation QLC NAND flash memory and 8th-generation TLC NAND flash memory. Our Norns can achieve superior optimization over existing post-fabrication optimization techniques by showing significant performance and reliability improvements by up to 8.8% and 12% on average, respectively.

When multiple apps with different I/O priorities share a high-performance SSD, it is important to differentiate the I/O QoS level based on the I/O priority of each app. In this paper, we study how a modern flash-based SSD should be designed to support priority-aware read performance differentiation. From an in-depth evaluation study using 3D TLC SSDs, we observed that existing FTLs have several weaknesses that need to be improved for better read performance differentiation. In order to overcome the existing FTL weaknesses, we propose ReadGuard , a novel priority-aware SSD management technique that enables an FTL to manage its blocks in a fully read-latency-aware fashion. ReadGuard leverages a new read-latency-centric block quality marker that can accurately distinguish the read latency of a block and ensures that higher-quality blocks are used for higher-priority apps. ReadGuard extends an existing suspend/resume technique to handle collisions among reads. Our experimental results show that a ReadGuard -enabled SSD is effective in supporting differentiated read performance in modern 3D flash SSDs.

Although lateral charge spreading is considered as a dominant error source in 3D NAND flash memory, little is known about its detailed characteristics at the storage system level. From a device characterization study, we observed that lateral charge spreading strongly depends on vertically adjacent state patterns and a few specific patterns are responsible for a large portion of bit errors from lateral charge spreading. We propose a new state encoding scheme, called TailCut, which removes vulnerable state patterns by modifying encoded states. By removing vulnerable patterns, TailCut can improve the SSD lifetime and read latency by 80% and 25%, respectively.

To minimize unnecessary data movements from storage to a host, processing-in-storage (PiS) techniques, which move a compute unit to storage, have been proposed. In this position paper, we propose an extreme version of PiS solutions, called a processing-in-flash (PiF) scheme, that moves computation inside flash chips where data are physically present. As a key building block of a PiF solution, we present a novel flash chip architecture, CoX. Using a prototype PiF SSD based on CoX chips, we demonstrate that PiF-based SSDs are promising in accelerating data-intensive applications.

Bulk bitwise operations, i. e., bitwise operations on large bit vectors, are prevalent in a wide range of important application domains, including databases, graph processing, genome analysis, cryptography, and hyper-dimensional computing. In conventional systems, the performance and energy efficiency of bulk bitwise operations are bottlenecked by data movement between the compute units (e.g., CPUs and GPUs) and the memory hierarchy. In-flash processing (i. e., processing data inside NAND flash chips) has a high potential to accelerate bulk bitwise operations by fundamentally reducing data movement through the entire memory hierarchy, especially when the processed data does not fit into main memory. We identify two key limitations of the state-of-the-art in-flash processing technique for bulk bitwise operations; (i) it falls short of maximally exploiting the bit-level parallelism of bulk bitwise operations that could be enabled by leveraging the unique cell-array architecture and operating principles of NAND flash memory; (ii) it is unreliable because it is not designed to take into account the highly error-prone nature of NAND flash memory. We propose Flash-Cosmos (Flash C omputation with-O ne-S hot M ulti-O perand S ensing), a new in-flash processing technique that significantly increases the performance and energy efficiency of bulk bitwise operations while providing high reliability. Flash-Cosmos introduces two key mechanisms that can be easily supported in modern NAND flash chips: (i) M ulti-W ordline S ensing (MWS), which enables bulk bitwise operations on a large number of operands (tens of operands) with a single sensing operation, and (ii) E nhanced S LC-mode P rogramming (ESP), which enables reliable computation inside NAND flash memory. We demonstrate the feasibility of performing bulk bitwise operations with high reliability in Flash-Cosmos by testing 160 real 3D NAND flash chips. Our evaluation shows that Flash-Cosmos improves average performance and energy efficiency by $3.5 \times /32 \times$ and $3.3 \times /95 \times$, respectively, over the state-of-the-art in-flash/outside-storage processing techniques across three real-world applications.

3D NAND flash memory with advanced multi-level cell techniques provides high storage density, but suffers from significant performance degradation due to a large number of read-retry operations. Although the read-retry mechanism is essential to ensuring the reliability of modern NAND flash memory, it can significantly in-crease the read latency of an SSD by introducing multiple retry steps that read the target page again with adjusted read-reference voltage values. Through a detailed analysis of the read mechanism and rigorous characterization of 160 real 3D NAND flash memory chips, we find new opportunities to reduce the read-retry latency by exploiting two advanced features widely adopted in modern NAND flash-based SSDs: 1) the CACHE READ command and 2) strong ECC engine. First, we can reduce the read-retry latency using the advanced CACHE READ command that allows a NAND flash chip to perform consecutive reads in a pipelined manner. Second, there exists a large ECC-capability margin in the final retry step that can be used for reducing the chip-level read latency. Based on our new findings, we develop two new techniques that effectively reduce the read-retry latency: 1) Pipelined Read-Retry (PR²) and 2) Adaptive Read-Retry (AR²). PR² reduces the latency of a read-retry operation by pipelining consecutive retry steps using the CACHE READ command. AR² shortens the latency of each retry step by dynamically reducing the chip-level read latency depending on the current operating conditions that determine the ECC-capability margin. Our evaluation using twelve real-world workloads shows that our proposal improves SSD response time by up to 31.5% (17% on average)over a state-of-the-art baseline with only small changes to the SSD controller.

As data privacy and security rapidly become key requirements, securely erasing data from a storage system becomes as important as reliably storing data in the system. Unfortunately, in modern flash-based storage systems, it is challenging to irrecoverably erase (i.e., sanitize) a file without large performance or reliability penalties. In this paper, we propose Evanesco, a new data sanitization technique specifically designed for high-density 3D NAND flash memory. Unlike existing techniques that physically destroy stored data, Evanesco provides data sanitization by blocking access to stored data. By exploiting existing spare flash cells in the flash memory chip, Evanesco efficiently supports two new flash lock commands (pLock and bLock) that disable access to deleted data at both page and block granularities. Since the locked page (or block) can be unlocked only after its data is erased, Evanesco provides a strong security guarantee even against an advanced threat model. To evaluate our technique, we build SecureSSD, an Evanesco-enabled emulated flash storage system. Our experimental results show that SecureSSD can effectively support data sanitization with a small performance overhead and no reliability degradation.

3D NAND flash memory exhibits two contrasting process characteristics from its manufacturing process. While process variability between different horizontal layers are well known, little has been systematically investigated about strong process similarity (PS) within the horizontal layer. In this paper, based on an extensive characterization study using real 3D flash chips, we show that 3D NAND flash memory possesses very strong process similarity within a 3D flash block: the word lines (WLs) on the same horizontal layer of the 3D flash block exhibit virtually equivalent reliability characteristics. This strong process similarity, which was not previously utilized, opens simple but effective new optimization opportunities for 3D flash memory. In this paper, we focus on exploiting the process similarity for improving the I/O latency. By carefully reusing various flash operating parameters monitored from accessing the leading WL, the remaining WLs on the same horizontal layer can be quickly accessed, avoiding unnecessary redundant steps for subsequent program and read operations. We also propose a new program sequence, called mixed order scheme (MOS), for 3D NAND flash memory which can further reduce the program latency. We have implemented a PS-aware FTL, called cubeFTL, which takes advantage of the proposed techniques. Our evaluation results show that cubeFTL can improve the IOPS by up to 48% over an existing PS-unaware FTL.

Recent advances in flash technologies, such as scaling and multi-leveling schemes, have been successful to make flash denser and secure more storage spaces per die. Unfortunately, these technology advances significantly degrade flash's reliability due to a smaller cell geometry and a finer-grained cell state control. In this paper, we propose a state-aware reliability optimization technique SARO), new flash optimization that improves the flash reliability under diverse scaling and multi-leveling schemes. To this end, we first reveal that reliability-related flash errors are highly skewed among flash cell states, which was not captured by prior studies. The proposed SARO exploits then the different per-state error behavior in flash cell states by selecting the most error-prone flash states (for each error type) and by forming narrow threshold voltage distributions(for the selected states only). Furthermore, SARO is applied only when the program time gets shorter because of flash cell aging, thereby keeping the program latency unchanged. Our experimental results with real MLC and TLC flash devices show that SARO can reduce a significant number of flash bit errors, which can in turn reduce the read latency by 40%, on average.

Online document collaboration tools, such as Google Docs, offer designers different ways of communicating and working collaboratively compared to face-to-face interaction. In this paper, we attempt to explore the possibilities and limitations of using an online document collaboration tool for design problem-solving activities. A design workshop study was conducted to compare using Google Docs during a design task to face-to-face collaboration. As a result, we found different influences of exploiting an online document collaboration tool and face-to-face interaction on the design process, and identified the properties that afford different characteristics of design problem-solving activity. Based on these findings, we discuss the implications of using an online document collaboration tool and face-to-face interaction for collaborative design.

Recent NAND flash devices have large page sizes. Although large pages are useful in increasing the flash capacity, they can degrade both the performance and lifetime of flash storage systems when small writes are dominant. We propose a new NAND programming scheme, called erase-free sub-page programming (ESP), which allows the same page to be programmed multiple times for small writes. By avoiding internal fragmentation, the ESP scheme reduces the overhead of garbage collection for large-page NAND storages. Experimental results show that an ESP-aware FTL can improve the IOPS and lifetime by up to 74% and 177%, respectively.

The evolution of SNS applications has focused on the increasing pace of communication. Accordingly, adopting pause moment design for the SNS domain becomes significant, considering its worth for mental well-being and diversity of experience. Nonetheless, the vision is currently controversial, as it is lacking in attempts to examine the worth of pause moment design for SNS communication. Therefore, we discussed the benefits of pause moment design as an SNS application, based on the case of Ripening Room. From observation, we have identified three benefits of pause moment design; preserving room for solitude, expanding time experience, and providing additional indirect cues for communication. Nevertheless, the benefits also imply limitations of the current design, thus require following attempts to adopt a pause moment design for the SNS domain.

This study proposed some considerations for designing social media to encourage self-reflection of users, referring to rationales of exemplary case, --Ripening Room?. Ripening Room provides ripening time, a delay period between the time of writing and sharing posts, and a ripening score to evaluate users' self-reflection. To give insights for the design a preliminary exploration was conducted on university students about their perceptions and experience of self-reflection in social media. To evaluate the effect of Ripening Room's design, an empirical study on Ripening Room was conducted. Participants mentioned that the features of Ripening Room inspired them to self-reflect upon their thoughts, emotions, and behaviors. From the findings of the empirical study, further implications were suggested.

Interactive space has been suggested as a future direction for architectural development on the basis of technological advances, and the design factors that affect the user experience of space thus need to be explored. Motion is one of the critical means of affective expression for facial-constrained and verbal-constrained robots such as functional robots. This paper introduces an interactive robotic partition that recognizes a person around it and reacts to the person by expressing physical motions. Using the robotic partition, we conducted a 7 (type of motions: moving toward, moving away, expanding, contracting, incurving, outcurving, and trembling) × 2 (user perspective: approaching to the partition vs. sitting inside the partition) within-participants experiment (N = 28). Participants showed higher approachability to the space and greater preference for incurving and expanding motions than trembling motion. The results also showed an interaction effect between motion and user perspective. When the partition expressed moving toward and expanding motions, participants in a sitting perspective reported higher approachability and greater preference than participants with an approaching perspective whereas opposite results were revealed when the partition showed moving toward and contracting motions. Implications for design are discussed.

The objective of this study is to examine the effect of intergroup relations on robots through comparison with other objects. In an experiment, participants watched eight stimuli drawn from four types of objects (people vs. robots vs. animals vs. products) according to two types of intergroup relations (in-group vs. out-group) and rated each stimuli in terms of familiarity, reliability, and preference. Regarding familiarity and reliability, the effect of intergroup relations on robots was greater than that on animals or products, but smaller than that on people. The degree of the effect regarding reliability was larger than that regarding familiarity for all types of object. In the case of preference, the effects of intergroup relations between people and robots and between animals and products were similar, and the effect on people and robots was greater than that on animals and products.

This study describes preliminary research for designing a growing robot. To explore the interaction between a human and an object that changes physically through its growth, focus group interviews were conducted with participants who kept pets, plants, and a plant-like product. An appropriate target model for designing a growing robot, the value of raising living things, and the features of interaction that induce affinity were examined.

The objectives of this study are to investigate the usability of the anthropomorphic sound feedback for service robot malfunction and to suggest the design guideline. Two experiments were carried out in a laboratory setting and an actual home environment. Independent variables of the experiments were two types of feedback (anthropomorphic vs. non-anthropomorphic) and two types of malfunctions (catastrophic vs. warning). The usability comprising of effectiveness, efficiency, and satisfaction was evaluated through a questionnaire and video analysis. The results from the experiments were summarized as follows. First, the usability of anthropomorphic feedback was better than non-anthropomorphic feedback. Second, the feedback of warning malfunction displayed higher usability than the feedback of catastrophic malfunction. Third, non-anthropomorphic feedback had higher effectiveness and satisfaction on the catastrophic malfunction while anthropomorphic feedback was more effective and satisfactory on the warning malfunction. Based on the results, design guideline of anthropomorphic sound feedback for service robot malfunction was suggested.

The objective of this study is to suggest a design guideline to build a personality for an entertainment robot, ROLLY based on basic factors of motions and their interrelations. Independent variables were the direction at two levels, the speed, the volume, and repetition at three levels as the basic factors of a motion. Dependent variables were dominance and friendliness as personality factors. Eighteen motion samples were designed with two or three levels of independent variables through the use of the orthogonal array of Taguchi. Participants watched eighteen motion samples in a random order and evaluated the personality factors (dominance and friendliness) based on each motion sample on a seven-point Likert scale. The results of the evaluation yielded basic guidelines to express robot personalities using motions while controlling the direction, speed, volume, and rate of repetition.

The objective of this study is to express the four types of personality of a robot based on Myers-Briggs Type Indicator by controlling the size, speed, and frequency of the gestures of a robot and to examine userpsila impressions of the robot by controlling the gesture design factors. The independent variables were three gesture design factors (speed, velocity, and frequency) with two levels each, producing eight gesture types. The eight gesture types were presented in two robot positions, a speaking robot and a listening robot. Participants watched a total of 16 robot gesture samples and evaluated each sample on the personality of the robot and their impressions. The evaluation results provided basic guidelines to express robot personalities through gestures, describing specific methods to control the speed, velocity, and frequency of a gesture. In addition, it was found that personality expression of a robot through gesture and the control of gesture design factors affect user impression of a robot.

The objective of this study is to examine the desirable correspondence between a robot appearance and its interaction. Based on Bales’ Interaction Process Analysis (IPA), the four types of interaction were extracted; Agree , Question , Suggestion , and Disagree. An experiment was conducted with a 4 (robot appearance types from the previous research) × 4 (interaction types from IPA) within-groups factorial design. In the experiment, participants took part in a task that involved selecting colors corresponding to 16 given words with a robot. After completing each task, they evaluated each robot. The evaluation results on subjects’ impressions of the robot and on the relationship between a user and a robot provided the proper and improper matches between robot appearance types and interaction types. Both anthropomorphic and zoomorphic robots were well-matched with Agree or Question while they were ill-matched with Suggestion or Disagree, caricatured robots displayed a desirable correspondence with Agree while they showed improper correspondence with Question; functional robots were compatible with all interaction types except Disagree.

The objectives of this study are to examine the appropriate body features for four types of social robots and to explore how the elements of body feature affect subjects’ impressions of the robot. Five body feature elements were deduced from a literature review and a preliminary survey. Based on the extracted body feature elements, various robot samples were implemented with a robot kit. In an experiment, participants evaluated each robot on the appropriateness of the robot for the four types of social robots and their impressions of the robot. The evaluation results provided the appropriate elements of body feature with the proper number of each element for each type of social robot and explained how the body feature elements affect the impressions made on people by the robot. An anthropomorphic robot with one head, two arms and legs and a body was familiar and enjoyable such that it was suitable for intimate interactions with humans. A zoomorphic robot was distinctive with one tail and four legs, which made the robot more pleasant and interesting. A caricatured robot was composed of diverse body feature elements in order to reveal an unrealistic or cartoon-like image. A functional robot had no head or arms; instead, it effectively utilized a screen to supply various services.

This study was conducted to define the correlation of a person’s personality and that of a personal service robot’s and to determine the perception people have on a personal service robot’s personality: (1) Kind and friendly personalities were preferred in a personal service robot. This can suggest people’s perceptions of personal service robots, (2) in human-robot interaction, theories on human-human interaction or human-computer interaction did not apply. There were no preferences towards robots with similar or complimentary personalities to the user, (3) Difference in preference was shown according to the user’s personality types, (4) A higher preference towards feeling type robots when given orders was shown. This indicated user’s desire for a kind robot.

Summary form only given. As various applications of robot technology related to human life increases, research domains for designers include not only appearance design but also interaction design based on an understanding of HRI. Through interaction systems, the level of technology and stability is recognized in a different way from the real elements of robot mechanisms. Therefore, the role of interaction design is very important in the development of robots. Unfortunately, the robotics expertise required to build HRI systems interrupts designers to participate in the HRI design process. Furthermore, the enormous costs and time required to build even a simple moving appliance make it difficult for designers to plan for HRI experimentations. However, the HRI experiment framework described in tins discussion allows designers to create stimulus-response interfaces rapidly. An experiment framework helps with the creation of an initial HRI design strategy, leading to significantly better performance and less effort compared to a perfectly functioning prototype.

Studies on robotic emotions were mostly focused on facial expressions. However, in human emotion recognitions, biological signals were effectively applied in use. In this paper, we clarified the utility of biological signals as a way to express robotic emotion. We designed facial expressions and set up biological signals (heartbeat, respiration) to apply to the facial LED interface for expressing emotions. The results from two sets of experiment demonstrate that biological signals are closely connected to an arousal level and intensity of emotion. It also can be a distinctive element for emotion expression which is deficient only in facial expression.

The objective of this thesis is to suggest a design guideline for a teaching assistant robot by clarifying what images satisfy the role of a teaching assistant robot, and by finding out what elements of body feature epitomize such images. Images of teaching assistant robots were established from a literature review and factor analysis. And eight elements of body feature were extracted from human form. Robotic external form samples varied according to the elements of body feature, w hich w as modeled three-dimensionally. Children, who are the main users of teaching assistant robots, evaluated the 3D robot samples projected onto a wall in real size. The evaluation criteria were the role images of teaching assistant robots, demographic features about age and gender, preference, and appropriateness. The results of evaluation were analyzed by analysis of variance, and analysis of correlation. Finally, a design guideline for a teaching assistant robot was suggested based on the results of the experiment about the correlation between elements of body feature and role images.