Hardware-free collision detection and braking for securing drone propellers

Purpose The widespread use of drones among the general public has led to an alarming increase in accidents, some with lethal consequences. As drone blades are made from rigid materials and rotate at very high speeds, their impact with a human body can result in fatal injuries. Reliable collision detection combined with near-instantaneous braking of the drone’s rotor(s) can substantially lessen the severity of injuries sustained. The purpose of this paper is to achieve a safety solution which can be easily integrated into new products, or retrofitted into existing systems. Design/methodology/approach Through a proof of concept, this paper demonstrates the possibility of detecting a collision with a drone propeller absent any hardware modifications to the drone’s instrumentation. The solution relies on current-sensor readings, ordinarily used for monitoring the battery status of electrically actuated drones. The braking is achieved purely by reconfiguring the motor’s control strategy, without the need for additional hardware, as has been the case in previous works. Findings This paper demonstrates the possibility of detecting a collision with a drone propeller absent any hardware modifications to the drone’s instrumentation. Originality/value Compared to previous works which require installing additional hardware, the solution is purely software. This makes it very easy to integrate into existing systems or new products, at no additional cost. In experiments conducted on a prototype system, the solution was shown capable of detecting a collision and braking the motor in fewer than 20 ms. This allowed attenuating centimetre-deep cuts made to a piece of meat by an unprotected rotor to mere superficial scratches.

Pensions in the Greek Political Economy

This chapter examines pensions as a factor fuelling Greece’s crisis, as a consideration shaping its bailouts, and as a locus for future unease. The problem was not the absence of reform—there were repeated ineffectual changes before 2010. Nor was it due to structural faults—the system’s building blocks are familiar. A toxic mixture of narratives, between social insurance, government, and social pensions, encouraged fragmentation, transforming sectional privileges into future liabilities; pensions became a key instrument of clientelistic politics. During the crisis a new player, the Troika, reversed ‘Words without Action’ into ‘Action without Words’. The pension landscape after 2018 is characterized by a new system and a recalibration of pensions to restrain their level. Two-tier pensions are provided by a single entity, financed by uniform contributions, with high retirement ages for new retirees. The attempt to protect those close to retirement backfired and necessitated deep cuts in pensions-in-payment. When these were ruled unconstitutional, their place was taken by retroactive application of new system rules to all pensioners in 2016. Despite deep parametric changes, Greece chose institutional continuity over systemic change—opting for a monolithic state-run pay-as-you-go defined benefit pension system, reminiscent of the 1960s. The evolving system is called to overcome the legacy of broken promises, must prove politically durable but also conducive to growth. The last word on pensions may not have been written.

The Contracting State: Austerity and Public Services

This chapter focuses on the ‘contracting state’ under Cameron, and reviews developments in three major public services since 2010: health, education and welfare, paying attention to the way in which these reforms affect the agency of the people who rely on these services. The Conservative-led coalition that was elected in 2010 made deep cuts to public spending in an effort to bring down the deficit, which they argued would restore economic growth. In practice, sluggish growth over the next few years meant that the cuts to public spending and services were less harsh than planned. However, the distributional effect of the cuts was uneven, with lower income, working-age households suffering disproportionally. In England and Wales, in organisational terms, austerity meant an extension of quasi-market reforms – particularly in health and education – that had been a feature of UK public administration since the 1980s. Pressure to cut public spending was also passed down to local government, ‘hollowing out’ a significant area of public provision and constraining their agency.

FEMTOSECOND LASER SCRIBING OF SAPPHIRE AT WAVELENGTH 1040 AND 520 NM

Sapphire cutting is one of the largest markets in laser materials processing. Since sapphire is one of the hardest transparent materials its mechanical and optical properties made it the ideal choice for use in the production of various devices, such as LEDs and transistors, cover glasses of watches and mobile devices. Among existing laser- or diamond-based tools solutions, femtosecond laser scribing appear as a promising technology since this technology has the unique capacity to produce highly localized bulk modification owing to non-linear absorption. Sapphire cutting with solid-state lasers is well known for many years and has become a modern industrial process. However, achievable process speed and cut quality are still limited. The femtosecond laser scribing of sapphire was studied at wavelengths of 1040 and 520 nm, followed by wet etching in HNO3/HF solution to identify emerging defects. The morphology of the laser ablated sapphire surface was evaluated by scanning electron microscopy. It was shown that at the wavelength of 1040nm, the material was effectively removed from the surface; however, cracks on the surface were formed. The use of the second harmonic gave more accurate and deep cuts compared with the main frequency at the same conditions. At the wavelength of 520 nm, the cracks were formed anisotropically inside the volume of the material. Therefore, there is a potential application of the femtosecond laser scribing for the fabrication of sapphire-based devices.

Deep Cuts

This chapter examines the presence of Female Gothic concepts and identity positions in Misty. It focuses on the abject, the grotesque and the uncanny and discusses the ways in which these are informed by transgression and transformation. It argues that Misty’s use of the supernatural often twists these themes into metaphors for the experiences of a female teenage audience: for example through grotesque bodies, uncontrolled growth, and the exclusion of male characters. It demonstrates that the Misty serials in particular are often set in an uncanny atmosphere of mystery and provide a space for uncertainties about family figures and patriarchal authority to be explored. Outcomes are uncertain and the options available to the protagonists frequently comment on the limitations placed on women.