Programs / Tele-Learn-MecanumDrive

TeleOp // Student lesson

Tele-Learn-MecanumDrive

Mecanum Drive

Trace Tele-Learn-MecanumDrive from signed joystick inputs to four normalized motor commands. This lesson uses Start.blk, not a sensor-guarded replacement; it has no wall or vision stop. Read and calculate first. Any physical trial requires a separate supervisor review, secure support, and Driver Station STOP access.

The opening comment mentions left-motor reversal, but the actual setup reverses both left motors AND back-right. BRAKE is zero-power behavior, not a position lock. The enabled source flag is not approval to run this mounting-specific sample.

Start with a question

How can three requests, each no larger than 1, combine to demand more than one wheel can accept?

By the end, you can…

Translate joystick signs into forward, strafe, and turn requests.
Calculate a common normalization denominator without amplifying small inputs.
Predict all four mecanum powers and the effect of the held slow-mode bumper.
Distinguish commanded power, telemetry, physical speed, and stopping behavior.

Start learning Jump to Code Quiz Download Blocks (.blk)

Before running: Ask your supervisor first. Keep Driver Station STOP ready.

Read · predict · explain

Build the idea, one block at a time

Read these steps before exploring the full program. The numbered blue comments in the diagram link back to the matching step.

01Read all four directions, not just the comment

Blocks for Read all four directions, not just the comment — Actual Blocks for this section

Blocks to notice

set Direction
set ZeroPowerBehavior BRAKE
set Mode RUN_WITHOUT_ENCODER
set Power 0

The actual Blocks set front-left, back-left, and back-right REVERSE; front-right is FORWARD. Mirrored mounting motivates direction correction, but these settings need physical verification for this robot. All four use BRAKE and RUN_WITHOUT_ENCODER, then receive zero. BRAKE resists motion at zero; it does not actively hold an encoder position or guarantee no coast.

For example: Copying only 'reverse the left motors' misses the back-right setting. Equal positive commands are intended to produce shared forward motion only with the matching mounting and wiring.

Think first

Does RUN_WITHOUT_ENCODER make +0.25 an exact wheel speed?

Show Answer

No. It is a power request; battery, load, friction, and mounting affect actual movement.

02Separate initialization from active driving

Blocks for Separate initialization from active driving — Actual Blocks for this section

Blocks to notice

telemetry READY
waitForStart
while opModeIsActive

Setup and zero commands occur before waitForStart. That block waits for Driver Station START; joystick mixing lives inside the later active loop. The READY display is information, not permission from a safety system. This sample does not have a repeated sensor-preview INIT loop.

For example: A nonzero joystick during waitForStart is not yet processed by the drive loop, but START can immediately make that held request active.

Think first

Is it safe to leave a joystick held just because INIT requested zero?

Show Answer

No. Release controls before START; the active loop will read current stick positions.

03Give each joystick axis a signed job

Blocks for Give each joystick axis a signed job — Actual Blocks for this section

Blocks to notice

get LeftStickY
negate
get LeftStickX
get RightStickX
set speed 1

forward = -LeftStickY, strafe = LeftStickX, and turn = RightStickX. A pushed-up left stick reports negative Y, so negation makes forward positive. Positive strafe requests right; negative requests left. The loop resets speed to 1 each time before checking the bumper.

For example: LeftStickY = -0.60, LeftStickX = -0.20, RightStickX = +0.10 become forward +0.60, strafe -0.20, turn +0.10.

Think first

What forward value comes from pulling LeftStickY to +0.40?

Show Answer

forward = -0.40, a backward request.

04Scale while the bumper is held

Blocks for Scale while the bumper is held — Actual Blocks for this section

Blocks to notice

if LeftBumper
set speed 0.35
multiply speed

Holding LEFT BUMPER changes speed from 1 to 0.35 for this loop. Every wheel gets the same final multiplier, preserving the normalized command ratios. This is a held control, not a toggle, and it applies to turns as well as translation. A 35% command scale is not a guarantee of 35% measured speed.

For example: A normalized wheel request of -0.80 becomes -0.28 while the bumper is held, then -0.80 after release if the sticks have not changed.

Think first

Does releasing the bumper keep slow mode latched?

Show Answer

No. The next loop resets speed to 1 unless the bumper is held again.

05Measure combined demand without sign cancellation

Blocks for Measure combined demand without sign cancellation — Actual Blocks for this section

Blocks to notice

ABS forward
ABS strafe
ABS turn
add
set denominator

For example: forward = 0.60, strafe = -0.60, turn = 0.20 give denominator 1.40, not the signed sum 0.20.

Think first

For forward = 1, strafe = 1, turn = 0, what demand must the denominator account for?

Show Answer

2: the front-left and back-right numerators can reach +2 before division.

06Never divide small requests by a small bound

Blocks for Never divide small requests by a small bound — Actual Blocks for this section

Blocks to notice

if denominator < 1
set denominator 1
divide wheel numerator

Replace any denominator below 1 with 1. This prevents division by zero at neutral sticks and prevents a small request from being amplified. Larger combined demands use their original sum so all wheels shrink together rather than being clipped independently.

For example: With forward 0.20 and other inputs zero, the raw sum is 0.20 but the final denominator is 1; each wheel stays at 0.20 before speed scaling.

Think first

What denominator is used when all three inputs are zero?

Show Answer

1, yielding zero wheel powers without dividing by zero.

07Mix the signs for each wheel

Blocks for Mix the signs for each wheel — Actual Blocks for this section

Blocks to notice

FL = forward + strafe + turn
FR = forward - strafe - turn
BL = forward - strafe + turn
BR = forward + strafe - turn

Each numerator is divided by the same denominator and multiplied by speed. Positive strafe adds to front-left/back-right and subtracts from front-right/back-left; positive turn adds on the left and subtracts on the right. Roller placement plus verified motor directions turns these patterns into chassis motion. No sensor guard modifies these powers.

For example: forward = 1, strafe = 1, turn = 0, speed = 1 give FL 1, FR 0, BL 0, BR 1 after dividing by 2. With slow mode, FL and BR become 0.35.

Think first

For pure positive strafe 0.50 with no bumper, what are FL, FR, BL, BR?

Show Answer

+0.50, -0.50, -0.50, +0.50, in that order.

08Compare inputs with the final command

Blocks for Compare inputs with the final command — Actual Blocks for this section

Blocks to notice

telemetry addData
get motor Power
button displays
telemetry update

Telemetry reports forward, strafe, turn, speed scale, and each motor's Power property, plus raw button states. Motor Power here is the requested value, not measured RPM or a distance. update sends the display; it does not add obstacle protection. Displayed Start/Back/A/B/X/Y buttons have no drive-stop branch in this sample.

For example: Joystick forward can read 1 while FL motor power reads 0.35 because the bumper changed the final scale.

Think first

If telemetry says FL power 0.35, does it prove that wheel is rotating?

Show Answer

No. It proves a command value, not physical motion; a stall or wiring problem can still exist.

09Clear every motor on exit

Blocks for Clear every motor on exit — Actual Blocks for this section

Blocks to notice

opModeIsActive
set four motor powers 0

When the active loop ends, the final chain explicitly requests zero from all four motors. Driver Station STOP ends the OpMode; a displayed gamepad button is not a substitute. Zero command and BRAKE cannot guarantee instantaneous physical stopping, and a software exit chain is not an independent hardware emergency stop.

For example: An earlier diagonal request left FL and BR powered. Exit must clear those outputs as well as FR and BL.

Think first

Would zeroing only the front motors completely clear the previous drive request?

Show Answer

No. Back-left and back-right also need zero.

Try it without a robot

Make the math make sense

forward = -LeftStickY; strafe = LeftStickX; turn = RightStickX: Preserve the signed requests; only the controller's forward/back Y is negated.
D = max(1, |forward| + |strafe| + |turn|): Use one bound for all wheels; do not amplify small requests.
FL = s*(f+x+r)/D; FR = s*(f-x-r)/D; BL = s*(f-x+r)/D; BR = s*(f+x-r)/D: Here f is forward, x is strafe, r is turn, and s is 1 or held-bumper 0.35. These are power commands, not distances.

Use a notebook or talk through your answer with a partner. You do not need a robot to predict what these blocks will do.

1. Trace a mixed command

On paper use LeftStickY -0.60, LeftStickX -0.20, RightStickX +0.10. Calculate forward, strafe, turn, D, and FL/FR/BL/BR at speed 1 and 0.35. Which signs change when the bumper is pressed?

2. Compare common normalization with clipping

Use forward 1, strafe 0.50, turn 0.50. Calculate the four raw numerators and normalized powers. Compare with independently clipping each raw numerator to [-1,1]. Explain why the ratios differ.

3. Separate request from evidence

Make columns for INIT, START with neutral sticks, pure right strafe, bumper-held strafe, and STOP. Write requested powers and the observations you would need to verify movement. Explain why telemetry alone cannot certify a safe robot.

Full commented Blocks program

One source program, in one column. Calls connect any named helper routines; they are not separate programs. Click a numbered blue comment to return to its explanation.

Back to explanations Download Blocks (.blk)

Ask your supervisor before importing or running these Blocks. Viewing the program does not control the robot.

Section in context

Full Blocks program

FTC Blocks-to-Java for this segment. Generated from the selected source Blocks using FTC SDK generators, with an atan2 adapter matching the SDK's degree conversion where needed. This excerpt uses the original program's variables, devices, and methods; it is not standalone. Review the lesson's setup notes for required helpers.

For supervisors: 60-minute teaching plan & robot setup

Before the robot is used

Safety: This is a read-and-calculate lesson first. Enabled metadata does not authorize operation. For a separately approved demonstration, support the robot with all wheels clear, exclude hands and loose items, use an operator and a supervisor at Driver Station STOP, and stop promptly for unexpected direction or a stall. There is no wall guard. BRAKE does not eliminate coast; isolate power before touching the drivetrain.

Required hardware & dependencies

Four mecanum drive motors named front_left_drive, front_right_drive, back_left_drive, and back_right_drive; verify each configured name against its physical cable and wheel.
FTC Robot Controller, Driver Station, secure battery, and a notebook. Motor direction settings are specific to the source and mounting, not universal wiring instructions.
Paired gamepad with verified left-stick axes, right-stick X, and LeftBumper. Stable wheels-clear support for any separately approved demonstration.

Source identity remains Start.blk. It uses native FTC Blocks and the four exact drive-device names; no helper ZIP is supplied or implied. Review motor mounting, directions, controller mapping, and an approved wheels-clear test plan before any operation. This migration does not deploy or change a robot.

Robot setup checklist

Review Start.blk in the FTC Blocks editor without treating import as deployment. Resolve the four native motor devices; no separate MyBlocks helper is claimed.
Compare each actual direction: FL REVERSE, BL REVERSE, FR FORWARD, BR REVERSE. Check mecanum roller orientation and physical cable labels before authorizing a bench test.
Confirm RUN_WITHOUT_ENCODER, BRAKE, zero setup powers, neutral controls, and STOP access. Do not expect wall sensors or gamepad face buttons to stop this sample.

60-minute teaching sequence

0-10 min
Predict signs from joystick positions and compare the setup comment with all four Blocks.
Look for: Students notice the back-right reversal and distinguish BRAKE from a position hold.
10-25 min
Compute denominators for neutral, small, diagonal, and mixed inputs.
Look for: Absolute magnitudes do not cancel; small inputs use D = 1.
25-40 min
Trace wheel signs and repeat one calculation with the held bumper.
Look for: All four powers share the same denominator and scale.
40-60 min
Compare a paper telemetry table with the quiz and discuss a separately approved bench observation.
Look for: Requested power is not measured motion, and STOP clears all four outputs.

Observation notebook

Notebook: inputs, calculated commands, and separate physical evidence
Condition	f / strafe / turn	D / speed	FL / FR / BL / BR	Evidence or question
Small forward	0.20 / 0 / 0	1 / 1	0.20 / 0.20 / 0.20 / 0.20	Power request, not RPM
Diagonal, bumper	1 / 1 / 0	2 / 0.35	0.35 / 0 / 0 / 0.35	Why do two wheels receive zero?
Exit	Not used	Not used	0 / 0 / 0 / 0	Record coast only in an approved demonstration

Use paper traces unless a supervisor has separately approved hardware activity. Label motor Power readings as commands and physical movement as observations.

Troubleshooting · stop before investigating

A wheel appears to oppose the other wheels.: STOP; review the exact four direction settings, motor mapping, and roller orientation. Do not compensate with an invented mix before checking hardware.
Tiny stick movement predicts full power.: Inspect the denominator < 1 branch; D must become 1 rather than the small magnitude sum.
A wall does not change the command.: That matches this source: no wall sensor is read. Do not enable a separate study and assume it guards Start.
Power telemetry is nonzero but the wheel does not move.: STOP and isolate power before inspecting wiring or a stall. A power property is not an encoder or motion measurement.

Exit ticket & assessment

Calculate pure positive strafe at 0.50.
Explain why D cannot be 0.20 for a 0.20 forward request.
Name the absent safety feature and the correct control for ending the OpMode.

Assessment: Require correct signs, a common denominator, held-bumper behavior, and a command-versus-motion explanation. Safety understanding includes no wall guard and all-four zero cleanup; correct arithmetic alone is not a pass.

Extension challenge: On paper compare common normalization and independent clipping for one mixed input. Propose a hardware-verification checklist without editing or deploying robot code.

Teacher key · discuss after students predict

Mixed-input practice

f = 0.60, strafe = -0.20, turn = 0.10; D = 1. Powers are 0.50, 0.70, 0.90, 0.30. At 0.35 they are 0.175, 0.245, 0.315, 0.105; signs do not change.

Normalization versus clipping

For 1,0.50,0.50, raw powers are 2,0,1,1. D = 2 gives 1,0,0.50,0.50. Independent clipping gives 1,0,1,1 and changes the ratios.

Safety and source fidelity

Back-right REVERSE is an actual setting. RUN_WITHOUT_ENCODER is direct power control; BRAKE is not a hold guarantee. Start contains no sensor guard.

Tele-Learn-MecanumDrive

By the end, you can…

Build the idea, one block at a time

01Read all four directions, not just the comment

02Separate initialization from active driving

03Give each joystick axis a signed job

04Scale while the bumper is held

05Measure combined demand without sign cancellation

06Never divide small requests by a small bound

07Mix the signs for each wheel

08Compare inputs with the final command

09Clear every motor on exit

Make the math make sense

1. Trace a mixed command

2. Compare common normalization with clipping

3. Separate request from evidence

Your turn

Before the robot is used

Required hardware & dependencies

Robot setup checklist

60-minute teaching sequence

Observation notebook

Troubleshooting · stop before investigating

Exit ticket & assessment

Teacher key · discuss after students predict

Mixed-input practice

Normalization versus clipping

Safety and source fidelity