踏板辅助系统(PAS)与手动节流阀.doc

Pedal Assist Systems (PAS) Vs Hand Throttles1 CommentIts a debate nearly as old as electric bicycles themselves. Which is better: a pedal assist system (PAS) or a hand throttle? There is, of course, no single correct answer. It all comes down to personal preferenceand how you plan to use your ebike. Below well discuss the advantages and disadvantages of each method to help you decide which is best for you. Spoiler alert: its probably a hand throttle.Pedal assist and hand throttles; Capulets and MontaguesWhen it comes to the issue of pedal assist systems and hand throttles, there are strong, outspoken proponents on each halfof the debate. Supporters of bothsidesstubbornly tout the benefits of their chosen system, rarelygetting along with the other side.But before we blindly start choosing sides and sharpening our pitchforks, lets learn aboutthe similarities and differences between pedal assist systems and ebike throttles.Pedal assist systems and hand throttles are both methods of controlling the speed of an ebike. PASs usually works with a sensor mounted on the bottom bracket or pedal crank arm that senses your pedal cadence (the better ones sense pedal torque instead of cadence) and indicates to the controller that its time to accelerate. Hand throttles are more like traditional motorcycle throttles in that they are mounted on the handlebar and are operated by a twisting action.Both pedal assist systems and hand throttles come in a number of different styles. The different types of hand throttles are mostly just physical interface differences that dont affect their outright function, while PASs come in a variety of formsand associated qualities.Hand throttles, due to their familiarity and was of use, were the original form of motor control when electric bicycleswere first developed. However, some countries (Im looking atyou,European Union) began passing laws regulating ebike functions and usage, including the requirement that the motor only work when the user is pedaling. In some places the laws even went as far as to outlaw hand throttles all together. This ushered in a new era of ebikes with pedal assist systems designed to fulfill the law and allow ebikes to be imported into as many countries as possible.Pedal assist, how does it work?The most common type of pedal assist system comprises a ring of magnets mounted on the pedal crank and a sensor fixed to the bottom bracket. As the pedal crank turns, the sensor reads the rate of pedaling. The faster the pedal cadence, the faster the controller will makethe motor to spin.This type of PAS comes with a major design flaw: the speed a rider is pedaling doesnt necessarily represent how much power he or she needs. On flat ground, faster pedaling usually means faster speed and thus more power needed. However, pedaling up a hill requires even MORE power, yet hill pedaling speed is very slow due to the lower speed. The result is an ebike that is woefully underpowered when climbing hills, negating perhaps the most important benefit of an ebike, hill climbing.Torque sensor pedal assistsystemsA much more recent system which has improved on the older pedal assist system is a torque sensor PAS. The torque sensor is usually mounted on either the pedal crank or near the rear dropout and measures the amount of torque being applied during pedaling.The amount of torque being applied nearly exactly matches the amount of power needed at any stage of bicycle pedaling, including acceleration, steady cruising and hill climbing. This means that a torque sensor PAS works much better than an old fashioned magnet sensor PAS. The difference youll experience during riding is like night and day. Not only will it make your bike feel a lot lighter on hills, it will make your wallet feel a lot lighter as well.A torque sensing bottom bracketEbike pedal assist advantagesBut why would someone choose a pedal assist system over a throttle or vice versa? One reason could be if you live in a country where ebikes with hand throttles are not allowed. Ive spent a few years living in Israel where the laws forbid ebikes with hand throttles from being imported. All the ebikes that come into the country come with the old fashioned cadence sensor PAS. Humorously, a lot of them come with a hand throttle in the same box but not connected to the bike. Even though it istechnically illegal, the user can easily slide the hand throttle onto the handle bar and plug inthe supplied wire, allowing use of both the PAS and hand throttle.Another reason for using a pedal assist system would be for somewho wants to ensure that he or sheare getting exercise while using anelectric bicycle. Due to the power and speed of most ebikes, many people find themselves rarely needing to pedal their ebike. In fact, unless I make a conscious effort to provide some good old fashioned assistance to my ebike, I often forget the pedals are there and simply use them as foot rests.A pedal assist system ensures that you always have to pedal, though not very hard, to get your bike moving. This keeps you from relying 100% on the motor and throttle, giving you some healthy exercise every time you use your ebike.Pedal assist: trouble in paradiseMany people, including yours truly, find pedal assist systems frustrating and annoying. I dont use my ebike for exercise. I have running shoes for that. When Im on my ebike its because I have somewhere Ive got to be. Im heading to work, making a delivery, running an errand or doing something that means Ive got to be moving. Thats not the time that I want to worry about pretending to pedal in order to trick my bike into working for me. I want a simple, responsive and fool-proof system that is going to power my bike exactly when and how much I want, and thats what a hand throttle is for.Often times pedal assist systems fail to operate smoothly, resulting in quick, jerking movements. If you just want to start rolling slowly, you can easily control your acceleration with a hand throttle. But if you try to use pedal assist, you wind up with a few seconds of delay from the time you start pedaling, then a jolt as the motor kicks in abruptly. Not ideal under any circumstances.So if you feel like you want to get some exercise, and youre afraid an electric bicycle can be counterproductive to that goal, a pedal assist system is likely a good choice for you. If you want to use your ebike like a motorcycle for some thrill-riding fun or utilitarian transportation, a hand throttle will make your life much easier.Note: while a compromise of having a hand throttle and a PAS together on a single e