Mechatronics Notes PDF

Lecture 1. - Sensor provide data to control system to make decisions - Sensors detect physical parameters - Sensors use electrical signals like voltage or current to describe signals from the physical world - Control systems use linear, time-invariant math models to repre...

Lecture 1. - Sensor provide data to control system to make decisions - Sensors detect physical parameters - Sensors use electrical signals like voltage or current to describe signals from the physical world - Control systems use linear, time-invariant math models to represent physical nonlinear varying systems with uncertainties and disturbances - Control systems should be simple, reliable and accurate by this is hard - SISO - single input single output, MIMO multiple input multi output - An actuator is a device employed by a control system to alter or adjust the environment (motors) - An actuator allows physical movement by transforming energy into mechanical force - Input -> Error Detector - > Controller -> actuator -> process -> Output -> sensor - Example of open loop (microwave, DC motor) - Example of closed-loop (person steering a car by looking at the road markings) - Disturbance rejection is often an external input in a controller diagram as external correcting is applied Lecture 2: - Digital systems are more flexible and easy to maket/mass produce - Analog systems are less complex and more reliable for applications like fail-safes - Digital systems are becoming cheaper, and smaller, consume less energy, and compute more power - these are driving forces in engineering - A microprocessor (CPU) is a single processor core that supports at least instruction fetching, and decoding data and executing commands - Needs input and output - A microprocessor is a part of a microcontroller - Microcontrollers normally has a singla processor core, memory blocks, digital IOs, Analog IOS, and other basic peripherals - Microcontrollers combine all the necessary elements (such as input, output and memory) to allow the microprocessor to process it - Arduino is open source microcontroller that uses C/C++, it is low-cost and powerful - Arduino has analog pins as well as digital pins - Analog signals are like a sine wave, and digital signals are square waves - Adding shields can increase the amount of pins - Raspberry pi is a microcomputer that has an os, it uses ethernet, USB, micro HDMI and usb-c for power, it has bluetooth and wifi - Uses Raspbian (linux) - BCM (Broadcom SOC channel) - some pins are multipurpose (input/ output) - Pi can only have a limited amount of current flowing through it, motors cannot be connected directly - Pi only has limited inputs and output - Pi only uses digital signals and not analog - Pi requires a stable power source - Pi heats up quickly so heatsinks are required - SPI (Serial peripheral interface) allows a master with four bus wires to communicate with a slave, a clock wire is required. All chips share bus signals, eahc peripheral has its own chip select line - I2C (Inter-Integrated Circuit) communicates with low-speed peripherals. There are two signal lines (SCL - clock and SDA (carries clock signal) - data (for receiving data)) - The SDA acts are slave input and output on the I2C whereas on the SPI there are separate lines for that - SPI is faster than I2C, draws less power, is more expensive, more susceptible to noise - LCD runs on I2C Lecture 3: - AWG stands for american wire gauge - To interact with Raspebrry Pi analog signals need to be converted to digital using ADC - Digital devices are more difficult to debug as the values are 1 and 0 - Input devices - keyboard, mouse, stylus, touchsecreen, sensors - Output devices - screen, display, printer, speaker, LED - Push button will complete a circuit will its being pushed down - Limit switch does the same thing as push buttons, they were originally used to define the limits of the range of motion of objects - LED cathode (negative) is shorter than the anode(positive) - Buzzer vibrates when voltage is applied (piezo) - LCD (16x2) - Sensor ideal case is linear, however there is noise that makes it fuzzy and needs to be filtered - Torque = F x D - PWM affects average power by shortening and lengthening the interval between high and low (Longer low means less power) - Duty cycle = time on/(time on + off) D = PW/T * 100 - DC motor works through electromagnetism, stepper motors are DC motors with a feedback component (Potentiometer), Stepper motors half step and only certain coils are magnetized Lecture 4: - Chopper: DC-DC converter (Buck,boost) - Rectifier: AC-DC converter - Inverter: DC-AC convertor - Matri converter: AC-AC converter - Matrix converter = rectifier + inverter - Analog has an infinite number of increments - Digital signals are discrete (finite): there is a limited set of value through which they can be represented - Analog systems are exposed to noise and signal degradation especially over long distances - Analog signals are continuous, the prevision is limited by noise and quality of components - Small variations in Analog signals can lead to inaccuracies in measurement or control - Digital systems have delays due to signal conversion and processing - Digital systems need more energy to process and handle data - Digital systems are more complex to design and debug - Analog systems have infinite resolutions - Digital systems have limited resolution - Digital systems are easier to program and reconfigure whereas analog systems are faster and smoother real-time but harder to modify once implemented - For analog, 0.1% accuracy is good, for digital adding more circuitry increases accuracy - Analog max storage time is in minutes, digital max storage time is years - Faster circuits are analog, highest frequency circuits are analog - Analog designers need years of experience whereas digital designers can program easily - Hybrid systems use analog and digital components for example a sensor may produce analog data which is later converted to digital to be processed by a microcontroller - 1 or 0 is called bit, 4 bits is a nibble, 8 bits is a byte, a word is a group of bits that is a multiple of a byte - Binary simplifies the design of circuits, memory and data storage - Max number represented by n bits = 2^n - 1 - Min number of bits to represent a number = log2(Num + 1) (round up or down) - 1 = on/True 0 = off/false Lecture 5: - Tesla invented AC, Thomas Edison invented the light bulb - Edison brought Tesla in - Resistive load is normal, inductive load current lags by pi/2 (+pi/2), capacitive load current leads by pi/2 (-pi/2) - Active power (KW), power that powers equipment to perform useful work - Reactive power (KVAR), power that a magnetic equipment (transformer, motors, relay) needs to produce he magnetizing flux - Apparent Power (KVA) is the vector summation of KW and KVAR (Coffee + Froth) - ADC converts continuous analog signal to discrete digital values  - ADC allows digital systems to process real-world analog data (temp, voltage, pressure) - Signal conversion is done by sampling the analog signal at regular intervals and quantizing the sampled values into a finite set of data codes - Digitization is done by dividing the analog signal into discrete steps based on resolution. The more bits the ADC has, the finer the resolution and more accurate the representation of the original signal - Resolution is commonly 8-bit, 10-bit, 12-bit or 16-bit - Sampling rate is how frequently the ADC samples the analog signal in samples per second, the higher the more accurate - Input range is the voltage range of the ADC that defines the min and max voltages that the ADC can measure. Any voltage outside this results in inaccurate conversion - ADCs are sensitive to noise - ADCs, especially at high speeds, consume a lot of power - High speed ADCs may have less previsions, so you need to choose the in between - ADC applications: sensors, gather and process data, communication systems, control systems, audio and music - Quantizing the sampled signal is approximated to the nearest value within a range - Old ADC models used to have less bits than newer - New models can do GHZ processing for radar and video - New models are more power efficient - Higher performance ADC cost more - ADC converts analog signals to binary (encoding) - If the amplitude of the analog signal is above a certain value, it is considered a 1 - Step size (Q) = Voltagemax - Voltagemin / Nstates (Smaller is better) - Increasing resolution and sample rate improve accuracy - ADC voltage reading = Nstates/Voltage range X (Voltage - Voltage minimum) - ADC voltage reading = 1/Q X (Voltage - Voltageminimum) - To convert voltage to binary, get the reading value, round it, then divide by 2 - Nstates is 2^Nbits - Nyquist rule: Use a sampling frequency at least twice as high as the maximum frequency to avoid aliasing (effect that cause different signals to become indistinguishable when sampled, happens when input signal changes much faster than sampling rate) - Camera FPM vs RPM - Aliasing - Minimum sampling frequency >= 2 x frequency max Lecture 6: - Or gate with inverted inputs = and gate with inverted output - And gate with inverted input = or gate with inverted output - Or gate with inverted input and output = and gate - And gate with inverted input and output = or gate - Double not = yes - Kmaps are graphical method to simplify algebra expressions, they reduce number of logic gates required and optimize the circuit - Kmaps are useful for up to 4-6 variables  - - Each group should be as large as possible - Group 1s in straight lines up or down or on ends - Groups can overlap - Parity checker checks for possible error- can be even or odd checker - Parity checker counts if the total number of ones is odd or even to verify no errors Lecture 7: - Automation uses various control systems - Programming logic controllers have been available since 1960s - PLCs monitor the state of input devices, make decisions based on the input data and custom program, controls the state of the output devices, collect and share data to help identify which operations need adjustment - SCADA control system that monitors industrial processes and machines - Objective of automation is to bring added value to a set of raw materials to produce products of higher value - Requires: human intervention - Automation leads to reduced cost of labor and material saving, removal of hazardous work and safety issues, improved product quality and performance, high productivity and quality job creation - PLC is sequential - Example: add milk (Step 1) -> milk addition complete and high-fat cocoe in recipe (transition 1) -> ass high-fat cocao (step2) -> high-fat cocoa addition complete (transition 2) -> add cream (step 3) - There are 5 programming languages for PLCs Unstruction list, structure text, function block diagram, ladder diagram, sequential function chart - Hardware is connection through relays, electronic boards, switches: it is more reliable but not flexible for future changes - Software is obtained through programming: it is flexible for future changes but not used for important safety functions - Single protection: position switches or forced open contacts, manually check for periodic safety functions, overzixing of some components like relays and contactors - Single with supervision protection: In addition to some techniques mentioned above, security system must include a self monitoring function, failure detecting circuits made with contactors and relays  - Redundant protection: reduction or duplication of critical components/functions, combining the normally open and closed contact interlocks, combining different electrical and non-electrical systems - Redundant with supervision: in addition of a combination of different technologies as described above, a continuous supervision function might be added - Ladder logic: Before PLCs, ladder was used to describe automation technology made by using electromagnetic relays - Electromagnetic relays: Metal plate which is attracted to a coil when the solenoid is energized and pushed by a coil spring when de-energized, an electrical path through the normally closed contacts is created when non-energized a second path through the normally open is created when energized - Learn Ladder and PLC - Modern control objective: control the output, achieve robustness, change response characteristics - Static system: if a system does not change with time, it is called a static system - Dynamic system: If a system changes with time, it is called a dynamic system - A model is a simplified representation, reality is too complex to copy exactly but a lot of the complexity is irrelevant in problem solving - Black box model is system that produces results without revealing how it arrived at those results, only the input and outputs are known - White box model is a system when the input, output, and internal dynamics of the system is know - Spring-mass-damper system is a dynamic system - RLC circuit is a dynamic system Lecture 8: - Without feedback, a control system is highly sensitive to disturbances - Closed loop control systems decrease sensitivity of variation, reject disturbances, attenuate measurement noise, reduce steady state error, ease the control and adjustment of the transient response of the system - A stable system returns to its original position after a disturbance - Normal system has neutral stability - Linear system satisfies the properties of superposition and homogeneity - The superposition principle states that for all linear systems, the net response caused by two or more stimuli is the sum of the response that would have been caused by each stimulus individually - The homogeneity principle states that the output is always directly proportional to the input. - Linear approximation is as accurate as the assumption of small signals is applicable to the specific problem - Step input, ramp input (integral), parabolic input (integral) - An optimum control system is when the system parameters are adjusted so that the index reaches an extremum commonly a minimum value - Process variable (PV) - system parameter that needs to be controlled (Temp, pressure, flow rate) - Sensor - used to measure the process variable and provide feedback to control system - The set point(SP) - desired or command value for the process variable (such as 100 degrees for temperature in oven) - Error (e) - the difference between the process variable and set point; used by the system to determine the action to take - Rise time - time to go from 10% to 90% if the steady-state or final value - Overshoot - the maximum amound exceed final value - Settling time - time to settle within a certain pertance of a final value - Steady-state error - difference between the process variable and set point - Error = sp-pv - PID controller has proportional, integral and derivative and is the sum of 3 parallel actions to generate a control output - Kp: proportional constant that accounts for present error value - Ki: Integral constant that accounts for historical error values - Kd: Derivative constant that accounts for future errors - PID is accurate, eliminates steady-state error, reduces overshoot and is widely applicable - Proportional controller is easy to implement and understand, quickly responds to large errors and provides consistent correct effort based on real-time errors. The system have residual error and if the proportional gain is too high, it can cause the system to oscillate - Integral action eliminates the effect of disturbances at steady-state - PI controller is simple, eliminates steady-state error. It has a slower response due to integral action, if the integral gain is too, it can cause oscillations - Derivitive is proportional to the rate of change of the error signal - Underdamped systems have oscillations and take a long time to return to equilibrium after an error - Overdamped systems don’t have oscillations and take a longer time to return to equilibrium - Critically damped does not oscillate and returns to equilibrium in the shortest time without overshooting - Proportional decreases rise time - Integral eliminates steady-state error - Derivative removes overshoot and oscillations Lecture 10: - A good design prioritizes value, efficient, asthetics and other factors - Good design push and pull door - The design process is iterative and it will loop back on itself - 1) Research: should consider problems and successes with existing solutions, be mindful of sources you are using - 2) Design requirements: One of the most important parts, get the requirements/problem definition. Ensure design meets expected functionality. - Customer requirements: overview of required functionality - Interal requirements: company or engineer makes more specific requirements for the functionality of components - Shall (Requirement): Must be implemented and must be testable - Will (Fact): A fact or declaration of purpose for the design - Should (Goal): Non-mandator and something to optimize - 3) Feasibility: Determines whether project should proceed to design phase. Project must be an achievable idea and within cost constraints - 4) Conceptual design: A concept study evaluates the pros and cons. It is done to minimize likelihood of error, manage costs, assess risks and evaluate potential success. A weighted trade study can be done as a numerical method to evaluate each design idea. It is about value. - 5) Conceptual design: Rough sketches to give context to conceptual ideas - 6) Preliminary design: Schematics, diagrams and layouts of the project provide early project configuration. The system may be broken down into subsystems which will be responsible for various tasks.  - 7) Detailed design: Using CAD programs, a more detailed design is created to both draft and simulate before prototyping. - 8) Verification and validation testing: Verification checks that a product meets specifications. Validation checks if the operational needs of the user are met. - 9) Production planning: Consists of planning how to mass produce the design. Which tools should be used? Determine the sequence of operations; ensure mass-produced products meet specifications (small changes in the power of motor and stuff). - Upfront (fixed) costs include investments for machinery, software licensing (typically recurring payments every year) - Operating (variable) costs include costs associated with manufacturing such as electricity, fuel, factor maintenance, materials for manufacturing - Weighted trade study: Assign weights to each design requirement (how important it is with a number), everyone in the group gives the requirement a score, the scores are averaged and then multiplied by the weight. The weights are then averaged. - Decision making: construct image, compile requirements, collect info, compare alternatives, consider issues, commit to a decision - You want the highest impact with the lowest effort Lecture 11 - Extraction is for metals like surface mining and underground mining - Coal is mined like metals - Oil and natural gas are both extracted by drilling a well - Plastic is created from natural and organic metals such as oil - Silicon is used in semiconductors - Silica sand is mined and is vastly available on beaches - Steps for processing metal: beneficiation, smelting (extract only metal), casting - Steps for processing plastics: petroleum is heated, combining monomers creates polymers, moulding - Obsolescence is a loss of utility of a product which arrises not due to physical deterioration but other facts - Technical obsolescence: components become irreplaceable due to changes in tech over time (Replacement parts are no longer available) - Cause: Rapid technological advancements - To mitigate technical obsolescence: extend product lifespan with modular components (easy to upgrade), have backwards compatibility, policy interventions such as government laws on recycling - Example of technical obsolescence (Typewriter to word, vinyl to mp3) - Function/use obsolescence: owner’s needs have changed, current product may not satisfy their needs - Aesthetic/Style obsolescence: no longer popular fashion, looks outdated - Economic obsolescence: a more cost-efficient way to achieve a goal (beyond economic repair) - Legal obsolescence: Laws prohibit use (air conditioner) Lecture 12 - Revolute joints - rotation - Prismatic joints - linear - Forward kinematic - given joint variable and dimensions of links determine position - Inverse kinematics - given end positions and dimensions of links determine joint variable (solution is not unique) - Accident prevention - safeguard operators from machinery or automation failures - Protection of equipment - reduce damage and wear to expensive mechatronics systems ensuring smooth operation - Compliance with regulation - safer standards and legal requirements must be met to avoid fines and ensure safety - Enhanced productivity: safe environments lead to more efficient operations with fewer disruptions - There is an in-between between high risk and low cost and low risk and high cost - Common hazards in mechatronics include electric shocks, moving parts, and automation - Fail safes are important, make sure system stops when fail safe switch is released to ensure that it is always working - Fault tree analysis (FTA) explains that having more fails safes decreases probability of complete failure