Franka Emika, insanlarla birlikte çalışmak üzere inşa edilmiş, Sami Haddadin tarafından tasarlanmış bir kuvvet algılama kontrol şeması ile donatılmıştır.
Robot, çeşitli görevleri yerine getirebilir. Bu görevler, konumlandırma, delme, montaj ve herhangi bir zeka gerektiren herhangi bir otomatik işi içerir. Franka Emika, Franka’yı tork kontrollü bir robot olarak sınıflandıran motorlarındaki kuvvetleri ölçmek için gerinim ölçer kullanıyor. Sadece küçük çarpışmaları tespit etmekle kalmaz aynı zamanda herhangi bir hasarı önlemek için de kullanılabilmektedir.
Let’s look in detail at the process of boiling a pure substance.
We’ll start out with a compressed liquid. We’ll say it’s water at 25 deg C. Moreover, let’s say it’s contained in a cylinder with a piston so that the pressure inside the cylinder is always at atmospheric pressure.
If we start heating up the cylinder, the water inside will expand slightly. The pressure will remain constant as the piston moves with the water’s expansion. Once we get to 100 deg C, the water exists as a saturated liquid – any additional heat will cause it to vaporize.
If we keep adding heat to it, things get interesting. The water will start to boil. It’s volume will increase drastically, but its temperature will remain the same. All the energy you’re putting into it is going into the phase change. The amount of energy it takes to go from a liquid to a vapor is called the latent heat of vaporization. (Similarly, the amount of heat it takes for a solid to melt into a liquid is the latent heat of fusion.) So while the water in your cylinder is in the process of boiling, it exists as a mixture of saturated liquid and saturated vapor. Its temperature will remain at a constant 100 deg C throughout the process. Although its apparent volume will increase, its specific volume – the volume per unit mass – will also remain constant.
Once all the water has been vaporized, if you continue adding heat to the cylinder, the water will start to rise in temperature again and its specific volume will start to increase. In this state, it exists as a superheated vapor.
The entire process we just described looks like this.
Note that this show temperature vs. specific volume for only one
pressure – if we varied the pressure as well, things would look quite
different. The interdependence of temperature, volume, and pressure will
be important in our analysis of thermodynamic processes.
We’ve spent some time going over the basics of heat engines and refrigerators. These are machines which manipulate a working fluid through some sort of cycle in order to move heat from one location to another. We have some idea of the overall way they work, but to really understand the details of what’s going on, we’re going to have to know a little more about how this working fluid behaves.
For right now, we’ll restrict our discussion to materials which qualify as pure substances. A pure substance has the same chemical composition throughout – all its molecules are the same. We’re all familiar with phases of matter – solid, liquid, and gas are the ones we see on a daily basis. Matter in solid form has its molecules arranged in a regularly structured lattice. In a liquid, molecules have about the same distance from each other as they do in a solid, but they’re not held in a structure and can move around each other freely, although their close spacing means that intermolecular forces play a large part in their motion. In a gas, molecules are widely spaced and careen about as they please, interacting with each other only through collisions.
For thermodynamics-related purposes, we’re really interested most in liquids and gases. Controlling the transition between these two states is the key to moving a lot of energy around. So let’s define some terms.
A compressed liquid or subcooled liquid is one that is in no danger of vaporizing.
A saturated liquid is one that is about to vaporize.
A saturated vapor is one that is about to condense.
A superheated vapor is one that is not in any danger of condensing.
Distinguishing between these is important from a thermodynamics because a fluid will have different properties related to its ability to absorb and release energy in each state. In coming articles, we’ll look a little more closely at the exact process of transition between phases.
We’re going to be looking more closely at amplifiers in the coming weeks. The specifics of how an amplifier is built can get pretty complex, so we’re going to want some kind of model that approximates the overall behavior of an amplifier and is simple enough for us to analyze relatively easily. Here’s a general one we can use:
This looks like a mess at first, but when you break it down, it’s not
so bad. The left side is the input to the amplifier. v_s is the signal
coming in. C_in and R_in represent the input impedance to the amp – that
is, the impedance the signal sees on its way in. v_in is the signal the
interior workings of the amp actually sees.
right side is the stuff coming out of the amp. The triangle on the left
is an imaginary voltage source that stands in for a lot of complicated
amplifier stuff for us. All it does is produce a voltage equivalent to
v_in multiplied by some internal gain, g. C_o and R_o here represent the
output impedance of the amplifier.
We’ll be doing a lot more with this model and others like it.
We’ve met amplifiers before in the form of op-amps. We’re going to see a lot more of them. In general terms, an amplifier makes a small signal bigger. But there’s some subtlety to this: not all signals are created equal. We’ve been looking at the effects of frequency on impedance, so we know that a signal of the same frequency will behave differently going through a capacitor than it will going through an inductor or a resistor. With what we know now, we have the power to create amplifiers that selectively boost some frequencies and attenuate others.
Let’s think a little bit about what this kind of amplification looks like. The kind of amp we’re all familiar with is an audio amp. If you’re amplifying an audio signal, you want all the stuff within human audible range (about 50 Hz – 15000 Hz) to be amplified equally. So the frequency response for your amplifier might look something like this:
A couple of things to notice about this graph. Gain is a unitless
number describing the ratio of the output to the input. So a gain of 100
means the strength of the output is 100 times the strength of the
input. The equation below shows a voltage gain, but you can also talk
about other kinds of gain.
Note also that the
frequency axis on the graph above is one a log scale. At the range of
frequencies we’ll commonly be dealing with, this is a necessity just due
to space constraints, but we’ll see later on that logarithmic graphs
can give us some interesting insight into amplifier behavior.
the amplifier in the graph above boosts signals within a range of about
50 Hz to 15 kHz more or less equally. It’s not perfect – you lose a
little at the extreme high and low ranges, but there’s a solid midband
letting most of the frequencies of interest come through. Suppose you
wanted to boost the bass of your audio. Bass frequencies run about 40 Hz
– 400 Hz. Your amplifier frequency response in this case might look
You might do this by chaining two
amplifiers one after the other – one for the bass, one for the rest of
the signal range. We’ll look more closely at the specifics of how to
make and analyze these in the coming weeks.
Perpetual motion machines are a perennial staple of fringe science. Many of them are very clever and seem, at first glance, as if they should work. If they did work, they would violate the laws of thermodynamics – you’d be getting energy for free. This video walks through a few simple ones and shows how they work. (Or don’t work.)