Fig.1 Why Visio Library Sucks

The advantages of the PitelSPOT Electrical Shape Library and the PitelSPOT Engineering Template are:

• Symbols align to a 0.1″  grid. This grid work great for those small double column articles required in IEEE journals and conference papers.
• The Engineering Template will setup the grids and snaps  for you. To use, go to File=> New=> New Drawing from Template=> then select PitelSPOTEngineeringTemplate.vst.
• Symbols are minimal. Use the connector tool to join shapes.

The presently supported shapes are shown in Fig. 2.

Fig. 2. List of Included Electrical Symbols

Version History

• 06-17-09: FREE DOWNLOAD: PitelSPOT Engineering Template for Visio Version 1.0
• 06-17-09: FREE DOWNLOAD: PitelSPOT Electrical  Shapes for Visio Version 1.0

The dowloads listed are for free. If  there is a symbol missing, make your request in the comments below. Bribes/gratitude in the form of donations are welcomed via the Paypal link below.

    - Single-Phase Grid Connected Control
    – Direct Digital Synthesis
    - All Digital Phase-Lock Loop
    - Software and Hardware in the Loop Experiments
    – Rapid Control Prototypes and System Products

 G. Pitel, “Fast power converters and rapid digital design,” UILU-ENG-2008-2509, CEME-TR-2008-02, December 2008, pp. 92-109.

This article covers chapters 1 and 2 of my disstertation. These chapters cover:

- Dissertation Introduction
- Voltage Source Buck Converter Modeling
- Boost Converter Modeling
- Voltage Source Inverter Modeling

G. Pitel, “Fast power converters and rapid digital design,” UILU-ENG-2008-2509, CEME-TR-2008-02, December 2008, pp. 1-14.

Hardware
Intel Core i7 2.66 GHz, 130W, Quad-Core with hyperthreading (8 core equivalent)
6 GB of DDR3 memory
two 1 TB  Hitachi hard drives
250 GB Seagate Barracuda hard drive
ASUS P6T Motherboard (16-phase VRM… covered in my dissertation)
rackmount case with 5 hot-swappable drive bays

Server Features
Shadow Copies – Every modification done to a file is backed up seamlessly. Can restore any intance of the file
Image Restoration – Recover entire OS and installed programs according to bi-weekly intervals
Off -Site Storage – Copy files to external hard drive and store offsite (when I remember).
RemoteApp - Load applications remotely within their own window. All application processing is performed on the server.
Consolidated Storage - All of Sheryl’s and my documents are stored in the same spot, regardless of which computer we use.
Virtual Machine Server - Emulate an entire computer in software

Web Applications
Wordpress Version 2.7
Gallery 2.3
Deki-Wiki Virtual Appliance
FTP Site

• Chapter 2: Piecewise linear, bilinear, and steady-state power converter models.
• Chapter 3.4: Minimum-time control / nonlinear-model predictive control.
• Chapter 3.5: Parameter system identification using recursive-least squares algorithm.
• Chapter 4: Programmable dc-dc converter system performance using active low/high-side damper resistors.
• Chapter 5: In depth study of  model-based techniques using a grid-interactive inverter.

I have contacted some city council members in hopes of bringing these enviroment- and energy-friendly vehicles to public streets. Below I am documenting the steps we have gone through so far, and will update it as new events occur. I encourage you contact your city council members to support NEVs in your town. This gesture is just a small step in ending our dependence on foreign oil. Thank you and I hope you find the items below useful.

NEV JOURNAL

• (08-12-08) Sheryl called our insurance agent to see if they would insure an NEV. They confirmed that they insure NEVs but at a higher rate than cars due to their lack of safty features and limited availability of replacement parts.
• (08-15-08) I contacted Champaign City Council, whose ordinances define where NEVs are allowed. The e-mail addresses and photos listed on the city council website suggested the members were very appoachable, and I found this to be true. Champaign also has an extensive database that lets users search previous minutes and agendas–an excellent resource for finding existing NEV ordinances.
• (08-18-08) I recieved a reply from a member of the city council saying he was adding NEVs to the agenda. He stated that he personally supports allowing NEVs on public streets but expects opposition for their use outside the University District, and recommends that I e-mail the other council members.
  
• (08-22-08) City council study session schedule approved for next week.
• (09-08-08) City council is discussing expansion on 09-09-08.
• (09-09-08) City council passed in favor of Neighborhood Electric vehicles eight to one. Stay tuned. Read the meeting summary (taken from the City of Champaign website).

Battery life is often measured by cycle life, the number of full charge/discharge cycles before the battery reaches 80% of its original capacity. Keeping the discharge current relative to the battery’s amp×hour capacity low and the discharge shallow improves battery longevity. Typical 12 V sealed lead acid (SLA) cells, like the ones found a Go-Ped, can be cycled 300 times. Here are a couple of tips about buying replacement batteries. Manufactures that do not advertise cycle life are probably not worth buying from, as they may use lower quality materials. Also, be wary of vendors that claim their cheaper batteries are “replacements for” and “perform similar to,” yet have no datasheets to back up these claims. As it turns out, Best Batteries (B&B) provides lots of data about their batteries, and come stock with Go-Ped Scooters. The ESR 750 contains B&B HR-9 batteries intended for high-discharge rates. The replacement battery should have the same width and length but a taller height and also be designed for high-discharge rates and high cycle life. Below is a summary for three different batteries meeting this size and discharge rate profile. All the data was taken from datasheets on the B&B website. I decided to get the EVP12-12 which I purchased locally from Brandt Services Inc. in St. Louis, Missouri, which had excellent customer service, reasonable prices, and dirt cheap shipping. The discharge rate was calculated from the Go-Ped’s specified distance, max speed, and from the stock battery’s discharge characteristics.

Scooter Cavity Extension

The Go-Ped scooter base needs modification if it is going to accommodate the larger batteries.  Much inspiration came from user Goped19 on GopedNation and battery discussions on V is for Voltage Forums.  The height was increased by stacking additional wood boards that mimicked the original base. I purchased one 24×24×0.75 inch thick piece of plyboard and drew two outlines using the original base as a template. Drill a large hole into each board and the cut the outline with a jigsaw, as shown Fig. 1.

Fig. 1 Cutting the outline

The boards were stacked, carefully aligned, then locked into position with aluminum tension wire. The board’s height makes straight drilling difficult. Use a drill press to make mounting holes. When the holes are done, the boards can be clamped together with a screw, nut, and washer. This is handy for keeping boards together when sanding the edges with a belt sander a wood file, as shown in Fig. 2.

Fig. 2 Cleaning up the woodwork

Finally, I connected batteries as outlined in a previous post and screwed down the board with 3.5 in. long, 0.25 in. dia., 20 count thread screw. The first trip to work was 3.8 miles with a 170 lb payload in econo-mode. I arrived with 60% remaining capacity according to the state-of-charge versus terminal voltage chart found in technical manual on the B&B’s website.

Two months into the internship I could not get to work any more. I opened the scoot scooter top to find 4 sealed-lead-acid (SLA) batteries with a pack configuration shown in Fig. 1.

Fig. 1. Stock Go-ped battery pack configuration.

From previous work I did with laptop batteries, I learned that manufacturers typically tie together parallel cells such that they form a pack similar to the one shown in Fig. 2, Step 4, which has two advantages. First, it halves the number of sensors that measure voltage. Measuring two voltages, one across B_1A and another across B_2A is essential for determining when to end charge and discharge, major factors that affect battery life. Unfortunately, the scooter model only measured the stack voltage, the total voltage across B_1A and B_2A. The second advantage is that it provides a balancing effect. If a cell becomes weaker, the adjacent cell gives it charge. Having cells reach end-of-charge and discharge in unison is the most beneficial situation. After two months my batteries were significantly damaged. I parallel tied my batteries, which allowed them to die more gracefully and it also gave me about 20% more range, both which helped me get to work and back until the end of the summer.

Fig. 2. Steps to extend Go-Ped pack configuration

IMPORTANT: Do not reconfigure the battery pack if you do not know what you are doing, and expect to void your warranty too. However if you want to take preventive measures follow these steps.

STEPS TO MODDING GO-PED BATTERY PACK

1. Find a well ventilated area to work in.
2. Disconnect the scooter from the charger and open the board with a torx screw driver.
3. Remove the four quick-connects at the top and bottom of the batteries.
4. Remove the two metal tabs that connect B_1A to B_2A and the one that connect B_1B to B_2B.
5. Create a wire harness that replaces the function of the metal tabs and will tie together the cells.
   1. You will need two short pieces of stranded 12 AWG wire and four yellow T2 female quick connect terminals and one long 18 or 22 AWG.
   2. Strip the wires and crimp both an the 18 AWG and the 22 AWG terminal into the same terminal.
   3. Crimp the other terminals so that the harness forms an H shape.
6. IMPORTANT: you must balance parallel batteries before you connect them together. Otherwise you will cause a spark and damage your batteries.
   1. Connect small resistors, about 100 Ω, between parallel batteries, and let them balance for a few hours.
7. Once balanced you can proceed to reconnect your pack.

The final connected harness should look something like the one in Fig. 3.

Fig. 3. Completed wire harness

Once you have made these modifications to you scooter there are some other life extension options to consider. Re-configuring the pack was a simple form of cell balancing, where charge moves between adjacent cells. There are commercial active cell-balancing products such as BattEQ and Power Cheq that moves charge from different levels of a stack. Check your scooter dimensions for free space. Another option is higher quality, larger capacity batteries. Ultimately I choose the last option, which I will discuss in another article and describe other scooter modifications.

UPDATE:
My wife and I have been able to get a couple rides into work this summer. We have been very happy with the new pack. I am able to ride 5 miles to work all on turbo mode . I measured the pack once, which indicated that this distance depletes the pack by 50%. I live in Illinois, which is as flat as you can get. I recently added some packaging foam around the batteries as the bigger batteries were causing a lot of road vibration. This easy mod made our rides a lot more comfortable.

My chain was starting to get stretched out from use. I tried to use my bike chain tool to remove some links, but Go-Peds chains are much smaller. I the bought the chain tensioner add-on for the scooter which works like a charm. Looking back, I should have built my own. $40 for a piece for plastic is a bit pricey.

Fig. 1 Buck converter with DCR

The buck converter circuit was simplified for analysis purposes by replacing the input and output with arbitrary voltage sources as shown in Fig. 2. The input voltage V_in(t) is a voltage signal produced by switching a dc voltage source. The input voltage passes through an LC filter, where L₂ is the inductor and R₂ its winding resistance. The inductor and output capacitor produce a filtered output signal V_out(t). The components in parallel with the inductor, R₁ and C₁, is the DCR network, which is chosen in such a way that the voltage v_C across C₁ is proportional to the inductor current i_L.

Fig. 2 Simplified Buck circuit

The circuit is further simplified by combining the network into parallel impedance, Z₁ and Z₂ as shown in Fig. 3.

Fig. 3 Parallel impedance network

The following derivation shows the mathematical relationship between R₁, C₁, R₂, and L₂ how to choose the RC network.

The voltage across C₁ is

(1)

and total input current is

(2)

where the total input impedance is

. (3)

The voltage difference term in (1) replaced with according to (2) gives

. (4)

Looking at the parallel impedance as a current divider, the inductor current is

(5)

Substituting (3) into (4)

(6)

then (5) into (6)

(7)

The DCR capacitor voltage is proportional to inductor the current by a factor K when

(8)

Which is the same as

. (9)

Thus when

(10)

(11)

and thus

(12)

To validate this mathematical relationship, the buck converter in Fig. 4 was simulated in Simulink™ and the results plotted Fig. 5. The parameter values for the circuit are E = 12 V, R₁ = 1 kΩ, C₁ = 1 μF, R₂ = 1 Ω, and L₂ = 1 mH. The circuit ran at a switching frequency of 100 kHz at 50% duty cycle.

Fig. 4. Simulink Buck converter model

Fig. 5. Simulated output