Safe Boundaries Research Articles

Reduced-dimensional MPC controller for direct thrust control

With the development of the aircraft gas turbine engine, a control system should be able to achieve effective thrust control to gain better operability. The main contribution of this paper is to develop a novel direct thrust control approach based on an improved model predictive control method through a strategy that reduces the dimension of control sequence. It can not only achieve normal direct thrust control tasks but also maximize the thrust level within the safe operation boundaries. Only the action of switching the objective functions is required to achieve the switch of these two thrust control modes while there is no modification to the control structure. Besides, a shorter control sequence is defined for multivariable control by updating only one control variable at every simulation time instant. Therefore, the time requirement for the solving process of the optimal control sequence is reduced. The proposed controller is implemented to a twin-spool engine. Simulations are conducted in the wide flight envelope, and results show that the average time-consumption can be reduced up to 65% in comparison with the standard model predictive control, and the thrust can be increased significantly when maximum thrust mode is implemented by using engine limit margins.

Harmless flirtations or co-creation? Exploring flirtatious encounters in hospitable experiences

Exploring the relationship between sexual harassment and service work in hospitality has long been considered a complex issue, due to the blurred and sometimes invisible line between flirting, harassment and the very nature of close contact hospitality service work. Little research has examined how mutual flirtations (when they are conducted in an appropriate manner and within safe boundaries) between customer and staff can play a positive role in the co-creation of hospitable experiences. This paper presents the findings of one theme from a wider PhD study which sought to explore the role of staff, customers and managers in the co-creation and performance of natural hospitable experiences. The focus of this paper is an exploration of the relationship between flirtatious encounters and the co-creation of hospitable experiences. In the wider study, three research phases were conducted. Semi-structured interviews were undertaken with service staff and managers from a range of hospitality servicescapes and data was gathered from customers through a number of focus groups, and the findings suggest that harmless and appropriate flirtatious encounters between customers and staff which are initiated in a natural and safe manner can have a positive influence on the co-creation of hospitable experiences.

Planetary boundaries and Veterinary Services.

National Veterinary Services (NVS) play a crucial role in animal health, production and welfare. They are also intimately involved with safeguarding global health security and the health of the planet. Climate change is just one of the nine planetary boundaries (PBs), i.e. Earth system processes, that can be used to monitor the vital signs of our living planet. In this paper, the authors identify the positive and negative impacts of humaninduced management of aquatic and terrestrial animals in relation to these PBs. In the context of NVS, the authors provide an overview of the real and potential impacts of NVS policies on Earth systems and offer suggestions as to how new sustainability paradigms may assist with reviewing and revising NVS mandates and facilitating stakeholder engagement. Opportunities are proposed for the World Organisation for Animal Health to contribute to the global debate on the role of aquatic and terrestrial animal agriculture and wildlife in sustainable development. In addition, the paper suggests that a wider debate is required in relation to recent significant increases in domestic animal populations and PBs. Intersectoral and interdisciplinary collaboration are required to achieve the transformation of the framework in which NVS operate. While such transformations cannot be driven by the veterinary profession alone, veterinarians have proven very effective operators in the One Health arena. By building on these intersectoral linkages, it will be possible for our profession and NVS to actively contribute to the crucial discussions and transformations required to pull Earth system metrics back within safe boundaries.

Preservation Rhinoplasty: Assessment of Anatomical Safe Boundaries on Computed Tomography.

Nasal dorsum reconstruction is a crucial step of the rhinoplasty. For avoiding complications, techniques that preserve natural dorsal anatomy becomes popular recently. In preservation techniques, ethmoidal bone surgery may take part in the vast majority of defined techniques. Therefore, detailed anatomical knowledge is essential to avoid severe complications, especially cerebrospinal fluid leakage. Based on these, this study aimed to investigate anatomical safe boundaries of preservation techniques based on the measurements on computed tomography. A total of 100 patients who underwent paranasal computed tomography were enrolled in this retrospective study. Five groups were selected based on the age distribution. The distance of the dorsal osteotomy line to cranial base, amount of cartilaginous/bony septum overlaps under nasal bones, cartilaginous/bony septum length anterior and posterior to the nasal hump starting point, and anteroposterior distance of perpendicular plate was measured. The mean distance between the starting point of the nasal hump and the cribriform plate was 29.5 mm. The amount of bony overlap above the cartilaginous septum was 10.9 mm in females and 10.5 mm in males. The length of septal cartilage posterior to nasal hump was 0 mm in 39 of 100 patients (39%) and the mean value was 2.38 mm in all populations. The mean distance from the starting point of the perpendicular plate to the cribriform plate was 28.17 mm. Perpendicular plate may take part in the constitution of the nasal hump. Therefore, delicate surgery with appropriate tools needed for avoiding the risk of skull base injury. Level of Evidence: 3 (Therapeutic).

Three-Phase State Estimation for Distribution-Grid Analytics

Power-distribution grids consist of assets such as transformers, cables, and switches, of which the proper utilization is essential for the provision of a secure and reliable power supply to end customers. Distribution-system operators (DSOs) are responsible for the operation and maintenance of these assets. Due to the increased use of renewable sources such as wind and solar, grid assets are prone to operation conditions outside safe boundaries, such as overloading, large voltage unbalance, and a rise in voltage. At present, distribution grids are poorly monitored by DSOs, and the above-mentioned problems may thereby go unnoticed until the failure of a critical asset occurs. The deployment of smart meters in distribution grids has enabled measurements of grid variables such as power, current, and voltage. However, their measurements are used only for billing purposes, and not for monitoring and improving the operating condition of distribution grids. In this paper, a state-estimation algorithm is proposed that utilizes smart-meter data for offline analysis, and estimates the loading of grid assets and power losses. Single- and three-phase state-estimation algorithms are compared through simulation studies on a real-life low-voltage distribution grid using measured smart-meter data. The three-phase state-estimation algorithm based on the nonlinear weighted least-squares method was found to be more accurate in estimating cable loading and line power losses. The proposed method is useful for DSOs to analyze power flows in their distribution grids and take necessary actions such as grid upgrades or the rerouting of power flows.

Personalized Trajectory Planning and Control of Lane-Change Maneuvers for Autonomous Driving

With the aims of safe, smart and sustainable future mobility, a personalized approach of trajectory planning and control based on user preferences is developed for lane-change of autonomous vehicles in this paper. First, a safe area during the lane change process is identified by using constraint Delaunay triangulation. Then, an improved rapidly-exploring Random Trees (i-RRT) is developed with B-spline to generate the feasible trajectory cluster, which is subject to the safe area boundaries and the vehicle dynamics. To extract a personalized trajectory from this cluster, we firstly adopt the fuzzy linguistic preference relation (FLPR) method to identify users' preferences on driving, which can be reflected by their subjective objectives including driving safety, ride comfort and vehicle stability. Then, the technique for order preference by similarity to ideal situation (TOPSIS) is utilized to solve the multi-objective optimisation problem formulated by considering the user preferences. The algorithms proposed above are integrated, and both simulation and experimental validation are conducted under lane-change scenarios of autonomous driving. Simulation and experiment results show that proposed approach is able to successfully realize personalized trajectory planning and lane-change control, satisfying users' various preferences and simultaneously ensure vehicle safety, demonstrating its feasibility and effectiveness.

Failure Mechanisms of the Wellbore Mechanical Barrier Systems: Implications for Well Integrity

Abstract Energy sustainability is the main motive behind the evolution of the concept of well integrity in the oil and gas industry. The concept of well integrity adopts technical, operational, environmental, organizational, and safety measurements to secure the energy supply throughout the life of the well. Technically, a high quality well performance can be maintained by establishing robust barrier systems that are responsible for preventing, controlling, and mitigating potential risks that could arise during the well life cycle. A barrier system is conventionally nested from one or multiple elements that act individually or collectively to scaffold the well integrity. The protection layers in a wellbore can be lost if the integrity of the barrier system is compromised according to the failure of one or all of its elements. Failure can be triggered by technical or non-technical factors. In this study, technical aspects that drive barrier failure mechanisms have given more emphasis. The failure mechanisms of the key mechanical barrier systems, such as casing strings, cement, diverters, blowout preventers (BOPs), production stream valves, and seal assemblies, have been thoroughly investigated. In this study, a comprehensive review of barriers failure mechanisms has been conducted to identify the roots of failures and to outline some of the essential safety measures adopted to avoid the loss of well control. The major findings of this paper revealed that well barrier systems are highly susceptible to failure in unconventional reservoirs, deep and ultra-deep offshore wells, and geothermal wells. The predominant failures identified are casing collapse resulting from cyclic loads, cement percolation by gas migration, cement carking by hoop stress, BOPs wear and tear promoted by frequent tests, and elastomeric materials disintegration caused by acidic gases. Considering these failure mechanisms while designing a wellbore can help the engineers improve the construction quality. In addition, it can assist the operation and maintenance crews in optimizing safe operation boundaries.

Spatially explicit boundaries for agricultural nitrogen inputs in the European Union to meet air and water quality targets

Agricultural production in the EU has increased strongly since the 1940s, partly driven by increased nitrogen (N) fertiliser and manure inputs. Increased N inputs and associated losses, however, adversely affect air and water quality, with widespread impacts on terrestrial and aquatic ecosystems and human health. Managing these impacts requires knowledge on ‘safe boundaries’ for N inputs, i.e., N flows that do not exceed environmental thresholds. We used a spatially explicit N balance model for the EU to derive boundaries for N losses and associated N inputs for three environmental thresholds: (i) N deposition onto natural areas to protect terrestrial biodiversity (critical N loads), (ii) N concentration in runoff to surface water (2.5 mg N l−1) to protect aquatic ecosystems and (iii) nitrate (NO3−) concentration in leachate to groundwater (50 mg NO l−1) to meet the EU drinking water standard. Critical N losses and inputs were calculated for ~40,000 unique soil-slope-climate combinations and then aggregated at country- and EU-level. To respect thresholds for N deposition, N inputs in the EU need to be reduced by 31% on average, ranging from 0% in several countries to 59% in Ireland and Denmark. The strongest reductions are required in intensive livestock regions, such as Benelux, Brittany and the Po valley. To respect thresholds for N concentration in runoff to surface water, N inputs need to be reduced by 43% on average, ranging from 2% in Estonia to 74% in the Netherlands. Average critical N inputs in view of the threshold for NO3− concentration in leachate to groundwater are close to actual (year 2010) inputs, even though leaching thresholds are exceeded in 18% of agricultural land. Critical N inputs and their exceedances presented in this paper can inform more targeted mitigation policies than flat-rate targets for N loss reductions currently mentioned in EU policies.

Strategic European Integration Scenarios of Ukrainian and Polish Research, Education and Innovation Spaces

A comprehensive study was conducted in the direction of research and institutional support and comparison with the nearest neighbour - Poland, to determine the current state and justify strategic scenarios for Ukraine's integration into the research, educational and innovation spaces of the EU as a source of proactive sustainable innovative development. Analysis of the use of foresight technology to determine the possible future, create the desired image of the future and determine strategies to achieve it using methods developed in various research areas revealed that its application makes sense in determining long-term factors, trends and directions of national economies. That is, in foresighting, in contrast to forecasting, the emphasis is made on qualitative rather than quantitative results, which does not provide the expected targeted policy of the state, because it does not give clear, concrete results of actions - quantitative strategic benchmarks, monitoring which would control the process of these areas' development. The disadvantages of foresighting methods that limit its application are identified. Scientific substantiation of strategic scenarios of European integration of Ukrainian and Polish research, education and innovation spaces is based on the concept of sustainable development, which is grounded on applied systems theory, management theory and economic cybernetics and comprises the stages of identifying and strategizing. Identification is carried out taking into account the definition of the safe existence boundaries and simultaneous norming and integrated convolution of indicators and thresholds of education and innovation. Comparison on one scale of integrated indices of education and innovation makes it possible to carry out the goal-setting stage, identify possible strategic development scenarios and build the desired development trajectories, i.e., to implement the principle of strategizing "the future is determined by the trajectory into future." Thus, knowledge of the desired values of integrated indices in each year makes it possible, through their decomposition by the method of adaptive regulation from the management theory, to justify the values of indicators that provide the desired growth trajectory and achieve certain goals of research, educational and innovative spaces of Ukraine and Poland.

Ultrasound Doppler examination in the surgical treatment of pituitary adenomas with cavernous sinus extension

Objective: To determine the effectiveness of intraoperative Doppler ultrasound in the surgical treatment of pituitary adenomas with invasive parasellar growth into the cavernous sinus Knosp 3 and Knosp 4. Material and Methods. During 2009–2017, 71 patients with pituitary adenomas (PA) with extension into the cavernous sinus Knosp 3 and Knosp 4 were retrospectively reviewed. According to the size PA were divided into pituitary macroadenomas, (from 10 to 40 mm) in 45 (63.4%) patients, and giant PA (over 40 mm) – in 26 (36.6%) patients. Cavernous sinus invasion Knosp 3 and 4 was identified in 47 (66.2%) and 24 (33.8%) patients respectively. Non-secreting PA - 43 (60.5%) patients and hormone-secreting PA - 28 patients (39.4%). Endoscopic endonasal trassphenoidal (EET) approach was used in all cases. Laterally expanded EET (LEEET) approach was used in 29 cases. Intraoperative Doppler ultrasound (IDUS) was used in 36 (51%) cases. Results. Intraoperative Doppler ultrasound was used in cases of Knosp 3 extension in 23 (32.4%) cases and in Knosp 4 - in 13 (18.3%) cases. Gross total resection, including extension into the cavernous sinus using IDUS was achieved in 22 (62.7%) patients. In cases where IDUS was not used, gross total resection was achieved in 19 (52.7%) cases. In cases where the IDUS was not used, recurrence rate was 7.3%, with IDUS - 5%. Biochemical remission was achieved in 22 (78.6%) cases. Liquorrhea nasalis after surgery was observed in 6 (8.4%) cases, meningoencephalitis - in 1 (1.4%) case, oculomotor palsy -3 (4.2%) cases. Conclusions. Intraoperative Doppler ultrasound is an informative method that provides safe resection of pituitary adenomas with cavernous sinus extension with a low level of possible postoperative complications. Parasellar extension of Pituitary adenomas into the cavernous sinus Knosp 4 significantly reduces the possibility of gross total resection. However, the use of intraoperative ultrasound makes it possible to determine safe boundaries for manipulation both medially and laterally from the internal carotid artery, increasing the level of radicality and the duration of clinical remission. Intraoperative Doppler ultrasound during endoscopic endonasal transsphenoidal surgery of pituitary adenomas with parasellar extension allows to identify the internal carotid artery in the tumor stroma with the existing changed skull base anatomy. Dura incision under intraoperative Doppler ultrasound reduces the risk of internal carotid artery injury.

An Overview of the Problems and Prospects for Circular Agriculture in Sustainable Food Systems in the Anthropocene

In this overview paper, we outline and explore problems and prospects for circular agriculture’s contributions to transformative change toward sustainable food systems in the Anthropocene. We define circular agriculture (CA) and provide historical context on its development. We then discuss how CA can contribute to food system transformations in four key areas: multi-functional landscapes; sustainable intensification (focusing on nitrogen/crop-livestock management and digital agriculture); smallholder farmers; and dietary change. We find that food systems transitions will be challenging due to the depth, scale, and speed of changes necessary for humans to remain within safe planetary boundaries out to 2050.

Evolutionary Plant Breeding as a Response to the Complexity of Climate Change.

SummaryClimate change is one of the processes that have already overstepped the safe planetary boundaries, together with the rate of biodiversity loss and human interference with the nitrogen and phosphorus cycles. The three processes are related to agriculture and, as such, to both food safety and food security, and ultimately to human health. Adaptation to climate change is a difficult breeding objective because of its complexity, its unpredictability, and its location specificity. However, one strategy exists, which is based on a more dynamic use of agrobiodiversity in agriculture through the cultivation of evolutionary populations. In this review, we show how the translation into agricultural practice of nearly 100 years of research on evolutionary populations and mixtures is able to address the complexity of climate change while stabilizing yield, decreasing the use of most agrochemicals, thus reducing emissions and producing healthy food.

Auditory Feedback Effectiveness for Enabling Safe Sclera Force in Robot-Assisted Vitreoretinal Surgery: a Multi-User Study.

Robot-assisted retinal surgery has become increasingly prevalent in recent years in part due to the potential for robots to help surgeons improve the safety of an immensely delicate and difficult set of tasks. The integration of robots into retinal surgery has resulted in diminished surgeon perception of tool-to-tissue interaction forces due to robot's stiffness. The tactile perception of these interaction forces (sclera force) has long been a crucial source of feedback for surgeons who rely on them to guide surgical maneuvers and to prevent damaging forces from being applied to the eye. This problem is exacerbated when there are unfavorable sclera forces originating from patient movements (dynamic eyeball manipulation) during surgery which may cause the sclera forces to increase even drastically. In this study we aim at evaluating the efficacy of providing warning auditory feedback based on the level of sclera force measured by force sensing instruments. The intent is to enhance safety during dynamic eye manipulations in robot-assisted retinal surgery. The disturbances caused by lateral movement of patient's head are simulated using a piezo-actuated linear stage. The Johns Hopkins Steady-Hand Eye Robot (SHER), is then used in a multi-user experiment. Twelve participants are asked to perform a mock retinal surgery by following painted vessels inside an eye phantom using a force sensing instrument while auditory feedback is provided. The results indicate that the users are able to handle the eye motion disturbances while maintaining the sclera forces within safe boundaries when audio feedback is provided.

Pituitary apoplexy: how to define safe boundaries of conservative management? Early and long-term outcomes from a single UK tertiary neurosurgical unit

Objectives (1) Describe presentation, management and outcomes of a single-centre series of patients with pituitary apoplexy. (2) Compare early and long-term outcomes of conservative and surgical management. (3) Identify predictive factors for visual recovery. Methods Retrospective analysis of patients acutely managed by Sheffield’s Neurosurgery over a 9-years period. Outcome comparison was made between 2 groups (‘conservative’ versus ‘emergency’) at early FU and 3 groups (‘conservative’ versus ‘elective’ versus ‘emergency’) at long-term FU. Results Data from 30 patients (M:F = 2.8:1; mean age: 54 years; median FU: 31.5 months) were collected. 86,7% patients presented with visual disturbances (70% acuity, 50% field, 50% diploplia). 10 (33%) patients underwent emergency surgery and further 8 underwent delayed elective surgery. At early FU, resolution rates of VA (33% versus 38%), VF (40% versus 50%) and CN deficits (71% versus 40%) were not significantly different between groups. At long-term FU, resolution of VA (80% versus 20% versus 75%) and CN deficits (67% versus 50% versus 80%) was not significantly different between groups. Most patients who underwent surgery presented with severe VA deficit (20% versus 40% versus 63%) but severity of initial deficit wasn’t correlated with long-term resolution. VF recovery rates showed significant difference between groups (p = 0.027): 67% versus 0% versus 88%. Endocrine outcomes were generally poor, regardless of the management strategy. Regarding possible predictive factors, age and tumour size correlated with visual outcomes. Especially in patients treated conservatively in the acute phase, no cases of complete resolution of VA or VF deficit were recorded when tumour was higher than 35 mm. Conclusions Good results are possible with conservative management in selected cases. Emergency surgery provides better visual outcomes. Decision-making process should be tailored to every single patient. We believe that a tumour vertical diameter >35 mm should tip the balance in favour of surgical management in presence of visual deficit.

System Kinematic Reliability Analysis for Robotic Manipulators Under Rectangular and Spherical Tolerant Boundaries

AbstractKinematic reliability is an essential index assessing the work performance of robotic manipulators. In general, the kinematic reliability of robotic manipulators is defined as the probability of the pose or position error falling into a specified tolerant region. Therefore, this work proposes an efficient method to conduct kinematic reliability analysis for robotic manipulators under rectangular and spherical allowable safe boundaries in terms of dimension and input uncertainties. First, based on the Baker–Campbell–Hausdorff formula and Lie group theory, the mean and covariance matrix of the distribution of the pose error are analytically determined. Then, the expectation propagation of the multivariate Gaussian and saddlepoint approximation method are employed to calculate the probabilities of kinematic reliability under the rectangular and spherical safe boundaries, respectively. The proposed method takes into account the boundness of the random error variable and is available for arbitrarily distributed errors. Finally, a spatial six degrees-of-freedom industrial robot is used as an example to demonstrate the effectiveness of the proposed method by comparison with other methods. The comparison results indicate that the proposed method has higher accuracy and efficiency.

Social Distancing, Safe Spaces and the Demand for Quarantine

Social distance has been a topic of interest in sociology for more than a century before the outbreak of the COVID-19 pandemic. Whereas in the past it referred to the distance between groups in more recent times it signifies the space between individuals. The aspiration for safe space and personal boundaries in recent years indicated that social distancing has acquired an increasingly individuated and privatised form. This article suggests that the demand for safe space can be interpreted as a demand for a quarantine from psychic threats. This pre-existing demand for a quarantine from criticism and pressure has seamlessly meshed with the imperative of social distancing in the COVID-19 era.

The Low-Carbon Imperative: Destination Management under Urgent Climate Change

To stay within the safe boundaries of global warming, the world now has 30 years to decarbonize its economy. This represents a very significant challenge for tourism as a growth system. Much attention has been paid to different tourism subsectors such as aviation, accommodation, and activities to reduce emissions, mostly on the basis of (future) technology. However, the Paris Agreement demands immediate action and significant year-on-year progress on a zero-carbon trajectory. This article discusses destination management under the new low-carbon imperative. It analyses challenges, including economic viability and resilience, that have also gained importance in light of the COVID-19 pandemic, and explores opportunities for better profitability on the basis of a leakage/spending value dichotomy proposition. The final section highlights the foremost role that destination managers must play in building prosperous and resilient low-carbon tourism destination systems and discusses the key insights for destination managers.

System for Assessing the Effectiveness of Temporary Blinding Devices

The development of non-lethal weapons and, in particular, temporary blinding devices is associated with problem of choosing boundaries of effectiveness. The aim of present work is determination of criteria for estimation of the effects of visual jamming devices action on the naked eye.The present-day scoring system used for effectiveness estimation of laser temporary blinding devices is based on maximum permissible exposure and/or accessible emission level defined for each hazard class in accordance with operating standard.In the present work we carried out analysis and modeling of the cases of application of temporary blinding laser devices. The proposed scoring system was founded on international standard IEC 60825-1-2014 as well as Manual on Laser Emitters and Flight Safety. The modeling of bright light action on observer eye was rested on CIE General Disability Glare Equation and provided quantitative description of jamming effectiveness. The main parameters used in this model and dictated by ambient light level and human eye characteristics, were veiling luminance and angle of distinguishing objects under it.In terms of exposition level and perception effects we determined six zones – unallowed, hazard, temporary blinding, discomfort, alerting, completely safe. Proposed system combined with modeling provides with visual demonstration of perceived light source and allows to describe human physiological sensation and to establish the fact of jamming at different distances. This system was the basis of the development of temporary blinding device for revelation of safe but effective spatial boundaries of action.

Environmental sustainability of European production and consumption assessed against planetary boundaries

The planetary boundaries (PBs) represent a well-known concept, which helps identify whether production and consumption systems are environmentally sustainable in absolute terms, namely compared to the Earth's ecological limits and carrying capacity. In this study, the impacts of production and consumption of the European Union in 2010 were assessed by means of life cycle assessment (LCA)-based indicators and compared with the PBs. Five different perspectives were adopted for assessing the impacts: a production perspective (EU Domestic Footprint) and four distinct consumption perspectives, resulting from alternative modelling approaches including both top-down (input-output LCA) and bottom-up (process-based LCA). Life cycle impact assessment (LCIA) results were assessed against LCIA-based PBs, which adapted the PBs framework to the LCIA indicators and metrics of the Environmental Footprint method (EF). Global environmental impacts transgressed several LCIA-based PBs. When assessing the overall environmental impacts of EU consumption compared to the global LCIA-based PBs, impacts of EU consumption related to climate change, particulate matter, land use and mineral resources were close or already transgressed the global boundaries. The EU, with less than 10% of the world population, was close to transgress the global ecological limits. Moreover, when downscaling the global PBs and comparing the impacts per capita for an average EU citizen and a global one, the LCIA-PBs were significantly transgressed in many impact categories. The results are affected by uncertainty mainly due to: (a) the intrinsic uncertainties of the different LCA modelling approaches and indicators; (b) the uncertainties in estimating LCIA-based PBs, due to the difficulties in identifying limits for the Earth's processes and referring them to LCIA metrics. The results may anyway be used to define benchmarks and policy targets to ensure that consumption and production in Europe remains within safe ecological boundaries, as well as to understand the magnitude of the effort needed to reduce the impacts.

Helicopter Safe Landing Trajectory after Main Rotor Actuator Failures

Main rotor actuator failure leads to catastrophic accidents for single main rotor helicopters. This paper focuses on safe landing trajectories after an actuator is locked in place by the remaining actuators, without introducing other control inputs. A general swashplate geometry is described, and new reconfiguration solutions for the control mixer are presented. The safe landing trajectories are obtained by formulating a nonlinear optimal control problem based on a nonlinear helicopter dynamic model and geometry constraints due to actuator failure. Safe landing trajectory results are shown with various initial forward velocities of all actuator failure cases. The safe initial speed boundaries are also explored by employing speed sweeps.