Noiseless and Vibration-Free Ionic Propulsion Technology for Indoor Surveillance Blimps

Transcription

1 Noiseless and Vibration-Free Ionic ropulsion Technology or Indoor Surveillance Blimps Ho Shing oon, Mark K. K. Lam, Maxwell Chow and Wen J. Li* Centre or Micro and Nano Systems, Faculty o Engineering The Chinese University o Hong Kong *Contact Author: wen@mae.cuhk.edu.hk Abstract We present in this paper a novel indoor blimp that is propelled by a propulsion technology that uses no moving mechanical parts and thus is noiseless and vibration ree. In our prior work reported at IEEE/ASME AIM 007, we demonstrated several prototype propulsive units (with asymmetric capacitor conigurations) that lit themselves into air. Using these basic propulsive units ( Ionic Flyers ), we have recently developed an indoor lying blimp that has a propulsion system with no moving mechanical parts and thus generates no noise or vibration -- the Ionic ropulsion Blimp. The key to successully create this novel indoor lying system is the development o a power generation system that includes an 11.1V battery which is capable o generating ~0kV DC voltage continuously over time or a load in the MΩ range. The architecture o this ionic power system will be presented. A detailed parametric analysis and an optimal design methodology o the Ionic Flyer are also discussed. Initial experimental results o the Ionic ropulsion Blimp are also summarized in this paper. Keywords: Ionic Flyer, Ionic propulsion, indoor blimp I. INTRODUCTION OWADAYS, miniaturized helicopters and planes Nembedded with sensing and control systems are widely used or indoor and outdoor surveillance missions. These lying systems use conventional aerodynamic principles to produce lit and thrust which has already been researched and understood or many decades. However, they require powerul rotating/moving mechanical parts in order to generate strong aerodynamic low or lit and propulsion. Thus, these lying systems generate signiicant noise during operation and may also unintentionally damage surrounding objects due to their rotating blades or propeller. As or surveillance missions, mechanical vibrations generated by moving parts such as the rotating rotors, blades, propellers make them unstable in terms o capturing pictures or videos in real-time. In this paper, we will present our group s undergoing development o a novel ionic propulsion technology that generates propulsive orce without using moving parts and generates no noise. Moreover, we will show that this propulsive technology is scalable. By increasing the physical dimensions o a basic propulsive unit, i.e., the size or designs o an Ionic Flyer appropriately, the propulsive orce could be increased accordingly. To demonstrate the potential application o this indoor ionic propulsion technology, an Ionic ropulsion Blimp is currently under development in our laboratory. It uses a helium blimp to balance the weight o the whole system and uses an Ionic Flyer to provide propulsion orce. The Ionic Flyer does not require any mechanical moving part and only use high voltage (usually higher than 10kV) to produce thrust. It converts electrical energy directly to mechanical energy or propulsion, and thereore, it does not contain any dangerous rotating/moving components which generate unwanted noise and vibration [1]. As a result, the Ionic ropulsion Blimp can operate silently and stably which will eventually beneit indoor surveillance applications. Fig. 1 shows the basic structure o the Ionic Flyer with wire-plate electrode coniguration (other conigurations were discussed in [1]). The parameters L, h, d, and r w represent the perimeter length, the collector height, the separation distance between electrodes and the radius o the emitter wire respectively. Fig. 1. The structure o Ionic Flyer with wire-plate electrode coniguration. The Ionic Flyer is basically an asymmetrical capacitor which uses air as the dielectric material. It contains two primary elements an emitter and a collector. The emitter is usually a thin wire which is connected to high voltage source, whereas the collector is typically a plate oil which is connected to ground. By applying a high voltage between two asymmetric electrodes, electric corona discharge will occur []. A high electric ield near the wire-emitter causes the surrounding air molecules to become ionized which partially breaks down to produce a high density o ions. As a result, the charged ions are drited towards the grounded plate-collector and this causes an electric current low between the electrodes. During the movement o ions, high requency collisions with neutral air molecules occurred. Momentum is transerred

2 rom the ionized gas to the neutral air molecules, resulting in movement o gas towards the collector. Thereore, thrust is generated by the Ionic Flyer rom plate-collector to the wire-emitter. I the input power is high enough, the output orce will balance its own-weight and thereore the Ionic Flyer can be lited up. Fig.. Illustration o the basic operational theory o the Ionic Flyer [1]. Since the Ionic Flyers needs a large high voltage (kv range) power supply to produce lit, it is impossible to make the Ionic Flyer to be an autonomous lying device due to the weight o the existing kv generation systems. On the other hand, the orce generated by Ionic Flyer is relatively weak compared to those using conventional aerodynamic principles. Thereore, the critical issues to be solved in order to make Ionic Flyer into an autonomous lying machine are 1) optimization o the design or the Ionic Flyers to produce lit orce, and ) miniaturization, weight reduction, and increased eiciency o a kv-range o high voltage (HV) power supply. Essentially, an analysis is required to understand the input-power to lit-generation eiciency o the Ionic Flyer based on the state-o-the-art HV power generation technology. II. ARAMETRIC MODELS OF THE IONIC FLYER Based on the liting phenomenon o Ionic Flyer, Chung and Li perormed systematic experimental analyses on Ionic Flyers with wire-plate electrode coniguration and introduced parametric models which are critical to the understanding o the operational principles o the Ionic Flyers [1]. The eects o all primitive parameters that aect the perormance o the Ionic Flyers have also been discussed by Chung in [3]. The Current-Voltage model or Ionic Flyers with wire-plate coniguration is derived as I = C ( L, d )( V V0 ( rw, d )) (1) where I is the input current in ma, V is the input voltage in kv, C is the current gain which is written as L C( L, d ) e () d where K e is the electrical environmental constant in ma/mm kv which relects the changes o the environmental conditions. V 0 is the onset voltage which is calculated by the modiied eek s equation and described as ( ) ( ) d V0 rw, d = G rw m0 g 0δ 1 + rw ln (3) δ rw rw where m 0 is irregularity o the wire, δ is the air density actor, g 0 is the breakdown ield strength, and G is the derived modiication actor with equation o r w ( ) ( r w ) = 1+ e. G (4) According to (1), it is shown the current and voltage is in quadric relationship. While the orce-voltage are in linear relationship and ormulated as F = J ( L, d )( V V ( V0 )) (5) where F is the generated orce in gram, V is the input voltage in kv, J is the orce gain which is written as L J ( L, d) (6) 0.54 d where K is the lit-orce environmental constant in g/mm 0.46 kv which depends on the environmental conditions. V is the barrier voltage which represents the minimum input voltage or the Ionic Flyer to create orce. It is related to the maximum power loss beore the Ionic Flyers is able to generate lit-orce and this power loss c is called Initial ower Dissipation (ID). It is ound to be proportional to the perimeter length L o Ionic Flyer and deined as c p L (7) where K p is the ID constant which represents the maximum power loss per unit length in the process o corona discharge. By substituting V into (1) and = IV, the ID can also be derived and V can be determined by c = CV ( V V0 ) p L (8) Finally, using the above equations, a third-order equation or the Lit-orce to ower Relationship is described by 1 1 = C( J F + V ( V ))( ( ) ) 0 J F + V V0 V (9) 0 where is the input power in Watt, F is the output orce in gram, and J -1 is the reciprocal o the orce gain J (reers to (6)). Using the Current-Voltage model, the Force-Voltage model, and the Force-ower model, the perormance o the Ionic Flyer with ixed structure under speciied voltage can be calculated. In other words, the structural design o the Ionic Flyer can be optimized by inding the maximum Force-to-ower ratio which is derived rom (1) and (5), as F ( V V 1.46 ( V0 )) / d (10) e V ( V V0 ) where K /e is the environmental constant, equal to K / K e. Using the above equations, based on engineering requirements, Ionic Flyers with optimal orce/power ratio can be obtained. Fig. 3 shows the parametric plot o (10) using empirical data collected by Chung and Li [1]. The

3 Ionic Flyers used to propel the Ionic ropulsion Blimp described in this paper were built using the design data rom Fig 3. Fig. 3. Variation o Force-to-ower ratio with gap distance and applied voltage. (K e = mA/mm kv, K = g/mm 0.46 kv ). III. DESIGN OF HIGH VOLTAGE OWER SULY In order to make the Ionic Flyer into an autonomous lying system, a small High Voltage power supply, which only weighs 80g, was developed. The power supply is capable o supplying DC high voltage o ~0kV under a wide range o load in MΩ range rom a single battery (~11.1V). Fig. 4 illustrates the basic coniguration o the power supply which is composed o 1) Battery, ) Step-up transormer, 3) Voltage multiplier, and 4) Control circuit. Fig. 4. The basic coniguration o the high voltage power supply. Fig. 5. (a) A conventional HV ower Supply which is usually used to operate Ionic Flyer as described in [7] and [8]. (b) The new battery-driven HV ower-supply developed by our group (1: Battery, : Control circuit, 3: Microprocessor + Bluetooth, 4: iezo Transormer, 5: Voltage Multiplier). A. Battery A single battery is used as the power source to the entire HV power supply, and thereore it should have a high energy density. By comparing the six most commonly used rechargeable battery, Lithium-ion olymer (Li-oly) battery has the best Weight-to-Energy ratio ( 6.1g/W h) among the other batteries [4]. The weight o battery can be calculated by Wb = Rb t (11) where R b is weight-to-energy ratio o the battery in g/w h ( 6.1g/W h or Li-olymer), is the output power in Watt, and t is the operation time required in hour. A 450mAh 3-cell Li-oly battery is used in the prototype which gives around 11.1V@1.A to the HV power system or about 0 minutes. B. Step-up transormer The step-up transormer can generate high voltage AC output rom a relatively low voltage. Conventionally, high requency coil transormer is used; however, those electro-magnetic transormers will generate high electro-magnetic intererence (EMI) which aects the wireless control and sensing system. The main disadvantage o the coil transormer is the heavy weight which diverges rom the objective o miniaturizing both the weight and volume o the power system, i.e., the weight-to-power ratio o coil transormer is high compared to the piezoelectric ceramic transormer which is used in our HV power system [5]. iezoelectric ceramic (ZT) transormer generates high voltage eiciently without any magnetic material, so it will only induce a very low EMI that does not aect the other components o the overall system. On the other hand, it is non-lammable and has an excellent weight-to-power ratio, usually less than 1g/W. The weight o the transormer can be ound by Wt = Rt (1) where R t is weight-to-power ratio o the transormer in g/w ( 0.864g/W or our design), and is output power required in Watt. C. Voltage Multiplier The output voltage o transormer is urther ampliied and rectiied by the Cockcrot Walton (CW) voltage multiplier in order to drive the Ionic Flyer. The CW circuit is made up o a voltage multiplier ladder network o capacitors and diodes to generate high voltage. Using only capacitors and diodes, it can step up a relatively low voltage to extremely high value, while at the same time being ar lighter and cheaper than a transormer. Besides, the voltage across each stage o the cascade is equal to twice o the peak input voltage, so eedback can be drawn rom the irst stage with potential divided in order to sense the output voltage o the power supply. Usually, the capacitance o the HV capacitors in CW circuit is not the issue o concern when designing a HV power supply, i.e., the perormance o the circuit does not depend on the capacitance [6]. However, it does aect the output when

4 the capacitance is low and the current output is relatively large. Fig. 6 shows the perormance o CW circuit using dierent capacitance or I out = 0.5mA. It shows that the capacitance should be large enough in order to drive a higher current with a better perormance. In our design, a silicone-sealed 10-stage CW circuit with 1000pF SMD HV capacitors is used or the HV power supply. The controller keeps the changed o driving requency when the output is increasing, i.e. Feedback1 is greater than Feedback0. Similarly, the driving requency will be restored when the output is decreasing, i.e. Feedback1 is smaller or equal to Feedback0, and the driving requency will be changed with opposite direction (increase or decrease) in the next iteration. Using this algorithm, the driving requency that gives maximum output, i.e. resonance requency, can be reached in a short period o time. Also, it will be kept tracked during operation in order to achieve the highest perormance or the HV power supply. Fig. 6. Output o CW circuit under dierent capacitances (I out = 0.5mA, V in peak = 1.5kV, and requency = 47kHz). D. Control Circuit The main objective o the control circuit is to convert DC voltage into pulsed DC voltage under speciied requency. To achieve this, an H-bridge switching algorithm is used. By sending the driving signal with small time delays, the input voltage will then be switched with speciied requency and input to the ZT. Fig. 7 describes how the current low through the ZT with dierent driving signals. Fig. 7. Current lows through the ZT with dierent driving signal using Full H-Bridge driving algorithm. ZT is required to drive under the resonance requency in order to get the highest step-up voltage gain, but the resonance requency will be shited during operation due to temperature and environmental change. Thereore, a resonance requency tracking system which compares the eedbacks rom the voltage multiplier is built into the control circuit. Initially, the driving requency is set near the resonance requency o the ZT. Once the controller enables the system, a high voltage will be generated and a eedback signal (Feedback0) will be received rom the multiplier. Ater that, the controller will start changing the driving requency in one direction (increase or decrease) and hence another eedback signal (Feedback1) will be received. By comparing magnitude o Feedback0 and Feedback1, the variation o output voltage due to the change o driving requency can be known. On the other hand, the control circuit also acts as a user control interace. It allows users to control the system wirelessly using Bluetooth Technology. Users can get the system inormation, enable the system and control the driving signal in order to control the output o the power supply. IV. ERFORMANCE OF HIGH VOLTAGE OWER SULY A. Varying the Frequency As the power supply generates high voltage with utilizing ZT, the output varies with the driving requency. Ater a parametric experimental study, the ZT is shown to perorm the best when resonance requency (about 46 khz) is reached. B. Varying the Duty Cycle The output voltage will also change with the duty cycle o the driving signal. Experimental analysis shows that the highest output voltage is achieved when duty cycle is 50%. Note that by tuning the duty cycle, the output voltage can be controlled. As the orce generated by Ionic Flyer depends on the applied voltage, the orce can also be controlled by tuning the duty cycle o driving signal. C. Eiciency During the step-up process, power is lost due to heat dissipation, corona discharge, or other environmental issues. Fig. 8 shows the eiciency o the power supply can be ound by plotting out the power input versus output. For our HV power supply, the eiciency is about 36 %. Fig. 8. ower input versus power output or various loads.

5 V. OSSIBILITY ANALYSIS OF ON-BOARD OWER SULY Many researchers or hobbyists aim to maximize the orce generated by Ionic Flyers in order to lit them with a sel-suicient on-board power supply, but never succeeded. The possibility can be analyzed systematically by using the parametric models which were described in Section II. Using orce-voltage model (5), the orce F generated by Ionic Flyer can be ound. Assume W is the total weight o the HV power supply, the total net orce F net will be F net = F W (13) I F net is greater than zero, it means that there is a net lit orce acting on the Ionic Flyer. In other words, the Ionic Flyer can be lit up with the on-board power supply. This can also be proved by inding the Net-Force-to-ower ratio (F net / ) to be greater than zero, as the ower is always a positive real number. Without loss o generality, power loss is ignored and only the essential components o a portable power supply, i.e. the battery and the step-up transormer, are counted as the total weight o the power supply. Using (5), (11), (1) and (13), the Net-Force-to-ower ratio is derived as F J ( V V ( V Rb t Rw net 0) = (14) By =IV and ater simpliication, (14) becomes F ( V V net ( V0 )) 1.46 ed Rb t R (15) / w V ( V V ) where K /e is the environmental constant, equal to K / K e. (lease reer to Section II or details). From the equation, the Net-Force-to-ower ratio only depends on the gap distance d, applied voltage V and the operation time t. To analyze the possibility o on-board power supply, we just assumed a short time, says 5 minutes, as the operation time, and thereore the Net-Force-to-ower ratio with various gap distance d and applied voltage V can be calculated. Fig. 9 shows the minimum gap distance and applied voltage in order to make the Net-Force-to-ower ratio greater than zero. Fig. 9. Net-Force/ower ratio with variable gap distances and applied voltages or t = 5min (K e = mA/mm kv, K = g/mm 0.46 kv, R b =6.1 g/w h, R t =0.864 g/w). 0 According to Fig. 9, in order to lit the Ionic Flyer with its on-board power supply even or only 5 minutes, it is required to have 163.9kV as the applied voltage with 1.35m as the gap distance between the wire and the plate. Such a high voltage output is impossible to generate rom a miniaturized HV power supply using the state-o-the-art technology (to the best o our knowledge ater extensive Internet search). Besides, the Net-Force-to-ower ratio is only g/w when ignoring the actual weight and power loss. Hence, to the best o our knowledge and based on the parametric equations, we can conclude that it is ineasible or the Ionic Flyer to lit up with an on-broad power supply (i.e., battery, transormer and circuits) using only the orce generated by Ionic Flyer. Thereore, the Ionic ropulsion Blimp is proposed and which is introduced in the next section to demonstrate a basic application o the Ionic Flyer. VI. IONIC ROULSION BLIM An Ionic ropulsion Blimp has been developed which can operate silently, stably, and does not contain any mechanical moving part. A helium blimp is used to generate auxiliary lit orce to balance the weight o the HV power supply and the Ionic Flyer that acts as a thruster to generate propulsion orce. In the near uture, an advanced control and navigation system will also be developed and deployed on the Blimp. Fig. 10. Illustration o the basic components o the Ionic ropulsion Blimp. A. Required volume o the blimp Helium is a noble gas which is stable, non-lammable and lighter than air. The liting orce F b o the helium blimp in gram can be calculated by F ( ρ ρ ) Vol ρ Vol (16) b = air He blim p where ρ air is the density o Air which is 1.9g/L, ρ He the density o Helium which is g/L, Vol is the volume o the blimp in L and ρ blimp is the density o the blimp which is about 0.4g/L or Mylar balloon. The total weight o the whole system is about 150g and the required volume o the blimp is ound to be 11L (7t 3 ) using (16). As a result, two 141.5L (5t 3 ) balloons are used to balance the weight o the system and the extra payloads. Fig. 11 shows the prototype o the Ionic ropulsion Blimp

6 which is used or the experimental results presented below. Fig. 11. rototype o the Ionic ropulsion Blimp. B. Experimental results o the Ionic ropulsion Blimp The Ionic ropulsion Blimp was shown to operate successul and some light tests were perormed. The accompanying video with this paper shows three tests or the ionic propulsion system. First is the liting test o an optimally designed Ionic Flyer which can lit up stably using the HV power supply developed by our group. Two red papers are used to show the air low generated by the Ionic Flyer. Second experiment shows the Ionic Flyer in horizontal coniguration which is the coniguration that they are mounted on the blimp. The test perormed shows how the Ionic Flyer operates in horizontal direction with various duty cycles o the driving requency. A orce gauge and an air low meter are used to monitor the output o the Ionic Flyer. It shows that about 6g orce with 0.7m/s air low is generated with 50% duty cycle. Finally, the Ionic Flyer with the entire power system is mounted on the blimp and a speed test is perormed. The control circuit is connected wirelessly with a user s computer using Bluetooth, so that the user can control the operation o the Ionic ropulsion Blimp. Ater enabling the movement, the Blimp moves orward silently and stably using the thrust rom the Ionic Flyer. The ollowing sequential pictures show the movement o the Ionic ropulsion Blimp. Time taken or each 0.5m is recorded and which shows that the blimp is accelerated rom 0.33m/s to 1.0m/s within 3.5s. Thereore, the orward acceleration is about 0.m/s. VII. CONCLUSION This paper presents a design methodology or optimizing the orce generated by the Ionic Flyer -- a novel thrust generation system that uses high voltage to give thrust without any mechanical moving parts. An extensive analysis was perormed to understand the power-input to lit-orce eiciency o the Ionic Flyer which showed that it is not easible to lit an individual Ionic Flyer by including its own on-broad power supply, given the state-o-the-art power generation technology. However, a light-weight, battery-driven, and miniaturized high voltage power supply was developed in order to allow the Ionic Flyer to be attachable and provide thrust to lying systems, e.g., a blimp. Thereore, an Ionic ropulsion Blimp (using the blimp as the auxiliary liting system) was developed and experiments were carried out to prove the operability o the Ionic ropulsion Blimp. In the uture, an advanced control and navigation system will be integrated onto the Blimp, which will also be capable o wirelessly transmitting a real-time surveillance video to a ground station. ACKNOWLEDGMENT The authors would like to thank Mr. Chung Chor Fung (currently with Virtus Asia Ltd., Hong Kong), who is the irst student in our group to develop the Ionic Flyer described in this paper, or his continual technical support and useul discussions on this project. REFERENCES [1] C. F. Chung and Wen J. Li, Experimental Studies and arametric Modeling o Ionic Flyers, 007 IEEE/ASME Int. Con. on Advanced Mechatronics, Zurich, Switzerland, September 007. [] L. B. Loeb, Electrical Coronas, University o Caliornia ress, London, England, [3] C. F. Chung, Experimental Studies on Electrical and Lit-orce Models o the Ionic Flyer with Wire-plate Electrode Coniguration, Mhil Thesis, Dept. o Mech. & Auto. Eng., The Chinese University o Hong Kong, China, 007. [4] I. Buchmann, What is the perect battery?, April 001, [5] M. A. Smith, J. McKittrick, and K. L. Kavanagh, iezoelectric Ceramic Transormer or Micro ower Supplies, Final Report or Micro roject [6] Y. Shikaze, M. Imori, H. Fuke, H. Matsumoto, and T. Taniguchi, erormance o a High Voltage ower Supply Incorporating a Ceramic Transormer, roceedings o the sixth Workshop on Electronics or LHC Experiments Krakow, oland, 11-15, September 000. [7] The JLN Labs. Available: [8] Blaze Labs Research. Available: Fig. 1. Movement o Ionic ropulsion Blimp.